Online Casino ‘Book of’ Slots
‘Book of’ is a mechanic of some video slots defined by a single dual-purpose symbol that functions as both wild and scatter while triggering free spins with randomly selected expanding symbols. ‘Book of’ slots share a core formula that has remained remarkably consistent since the original Book of Ra appeared in 2005: land 3 or more book symbols anywhere on the grid, receive 10 free spins, and watch one randomly chosen symbol expand across entire reels during the bonus round. This guide breaks down the ‘Book of’ mechanic, contrasts it with standard free spins formats, highlights the 10 strongest ‘Book of’ titles available, and shares practical tips for navigating their high-volatility profile.
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What ‘Book of’ Means in Online Slots
‘Book of’ is a slot feature built around a signature mechanic: a book symbol that serves dual duty as both the game's wild substitute and its scatter trigger. ‘Book of’ slots award free spins when 3 or more book symbols appear anywhere on the reels. Before the free spins begin, the game randomly selects one regular symbol to become a special expanding symbol for the entire bonus round.
Novomatic created the ‘Book of’ format with the release of Book of Ra in 2005. Novomatic's online division, Greentube, later brought Book of Ra to the digital market. The game introduced the expanding symbol mechanic that became the genre's defining feature: during free spins, the chosen symbol stretches to fill its entire reel whenever it contributes to a win, paying across all active paylines even on non-adjacent reels.
The format generated an entire subgenre. Play'n GO released Book of Dead in 2016, which became one of the most played online slots globally. Pragmatic Play, Stakelogic, Relax Gaming, Quickspin, and dozens of other providers have since released their own ‘Book of’ titles, spanning themes from Norse mythology and Greek legends to pirates and fantasy, while retaining the core expanding-symbol mechanic.
How the ‘Book of’ Mechanic Works: Step-by-Step
The ‘Book of’ mechanic centers on the free spins bonus round. The base game plays like a standard payline slot. The book symbol drives everything that makes the format distinctive.
- Spin the reels on a standard 5 × 3 grid with 10 paylines (most common configuration).
- Land 3 or more book symbols anywhere on the grid to trigger the bonus. The book pays a scatter win of 2x (3 books), 20x (4 books), or 200x (5 books) the total bet in addition to awarding free spins.
- Receive 10 free spins. Before the first spin, the game randomly selects one regular symbol to become the special expanding symbol.
- Play the free spins. Whenever the selected expanding symbol lands in enough quantity to form a win, it stretches to cover all 3 row positions on its reel.
- Collect payouts from the expanded symbols. Expanded symbols pay across all active paylines simultaneously, even on non-adjacent reels. This single mechanic is what produces the largest wins in ‘Book of’ slots.
- Retrigger if additional book symbols land during free spins. Most ‘Book of’ games award an additional 10 free spins, with no cap on retriggers.
A worked example illustrates the impact on payouts. A $0.10 bet on Book of Dead triggers free spins. The game selects the Pharaoh as the expanding symbol. Three Pharaoh symbols land on reels 2, 3, and 5. Each expands to cover its full reel. The expanded Pharaohs pay across all 10 paylines as scatter-style wins. The resulting payout reaches $15 on a $0.10 stake, a 150x return from a single free spin.
‘Book of’ vs Standard Free Spins: Key Differences
‘Book of’ slots and standard free spins slots both award bonus rounds, but the payout mechanics during those rounds diverge sharply. The expanding symbol mechanic is the central difference.
| Feature | Book of Free Spins | Standard Free Spins |
|---|---|---|
| Trigger symbol | Book (dual wild/scatter) | Separate scatter symbol (not a wild) |
| Free spins awarded | Typically 10 | Varies (5 to 25+) |
| Expanding symbol | Yes (randomly selected, persists for all spins) | Rare or absent |
| Expanded payout scope | Pays across all paylines, even non-adjacent reels | Pays on standard adjacent-reel paylines only |
| Retrigger mechanic | Same book symbol retriggers with no cap | Varies by game |
| Volatility tendency | High to very high | Low to high (varies) |
| Typical grid | 5 × 3 with 10 paylines | 5 × 3 with 10–50 paylines |
| Win concentration | Heavily concentrated in free spins | More evenly distributed between base and bonus |
‘Book of’ mechanic concentrates the largest payouts inside the free spins round because expanded symbols transform non-winning reel positions into paying ones. Standard free spins distribute wins more evenly across the base game and bonus rounds.
Top 10 Online Casino ‘Book of’ Slots
The 10 titles below represent the strongest entries in the ‘Book of’ subgenre, selected for expanding symbol execution, RTP, provider credibility, and sustained player popularity.
Book of Dead (Play'n GO)
Book of Dead follows the explorer Rich Wilde through ancient Egyptian tombs. Book of Dead is widely considered the benchmark Book of slot for online play, combining the classic expanding symbol mechanic with a 96.21% RTP and 5,000x maximum win that keeps it competitive against newer releases.
- Provider: Play'n GO
- RTP: 96.21%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Book of Ra Deluxe (Greentube / Novomatic)
Book of Ra Deluxe is the enhanced version of the original 2005 slot that created the entire subgenre. Book of Ra Deluxe retains the core expanding symbol mechanic on a 5 × 3 grid with 10 paylines, improved graphics, and a 95.10% RTP. The game remains a staple across European online casinos.
- Provider: Greentube (Novomatic)
- RTP: 95.10%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Book of 99 (Relax Gaming)
Book of 99 stands out with an unprecedented 99% RTP, the highest of any Book of slot on the market. Book of 99 adds a Wild Collection Feature where accumulating 99 wild symbols during base game play automatically triggers the free spins round, adding a secondary path to the bonus beyond the standard 3-scatter trigger.
- Provider: Relax Gaming
- RTP: 99.00%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Book of Tut Megaways (Pragmatic Play)
Book of Tut Megaways applies the Megaways engine to the ‘Book of’ format, producing up to 117,649 ways to win on a 6 × 7 grid. Book of Tut Megaways pairs the expanding symbol mechanic with variable reel sizes, creating a hybrid of classic Book of free spins and dynamic Megaways reel changes.
- Provider: Pragmatic Play
- RTP: 96.00%
- Volatility: High
- Grid: 6 × 7 (Megaways, up to 117,649 ways)
- Max win: 10,000x stake
Book of Shadows (Nolimit City)
Book of Shadows introduces a unique twist where players unlock additional rows, expanding from 5 × 3 to 5 × 4 in the base game and up to 5 × 5 during free spins. Book of Shadows charges a 50% stake increase for each row added, giving players direct control over grid size and volatility.
- Provider: Nolimit City
- RTP: 96.19%
- Volatility: High
- Grid: 5 × 3 (expandable to 5 × 5)
- Max win: 8,218x stake
Book of Atem WowPot (Games Global)
Book of Atem WowPot connects the Book of mechanic to a progressive jackpot network. Book of Atem WowPot retains standard expanding symbol free spins while adding four progressive jackpot tiers (Mini, Minor, Major, Grand) triggered through a random bonus.
- Provider: Games Global
- RTP: 92.02% (includes jackpot contribution)
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: Progressive jackpot
Book of Inferno (Quickspin)
Book of Inferno layers a symbol upgrade mechanic on top of the standard Book of formula. Book of Inferno marks random symbols during play, and landing enough marked symbols upgrades them on a meter, converting lower-paying symbols into higher-paying ones.
- Provider: Quickspin
- RTP: 96.15%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,846x stake
Book of Vikings (Pragmatic Play)
Book of Vikings shifts the genre's setting from Egypt to Norse mythology. Book of Vikings uses the classic 5 × 3 grid and 10-payline structure with expanding symbols, offering a 96.50% RTP and 5,000x maximum win.
- Provider: Pragmatic Play
- RTP: 96.50%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Legacy of Dead (Play'n GO)
Legacy of Dead is Play'n GO's sequel to Book of Dead, retaining the Rich Wilde universe and expanding the symbol mechanic. Legacy of Dead adds stacked wilds and the option for free spins to select multiple expanding symbols on retriggers.
- Provider: Play'n GO
- RTP: 96.58%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Book of Ra Magic (Greentube / Novomatic)
Book of Ra Magic refines the original formula by adding an additional expanding symbol with each retrigger, accumulating up to 9 expanding symbols across the bonus round.
- Provider: Greentube (Novomatic)
- RTP: 95.03%
- Volatility: High
- Grid: 5 × 3 (10 paylines)
- Max win: 5,000x stake
Pros and Cons of ‘Book of’ Slots
Online casino ‘Book of’ slots present 5 clear strengths and 5 notable trade-offs compared to slots with standard free spins formats.
| Aspect | Strength | Trade-off |
|---|---|---|
| Bonus impact | Concentrates the highest payouts in free spins through expanding symbols that cover entire reels | Delivers minimal returns during the base game, creating extended dry spells between bonus triggers |
| Simplicity | Maintains a clean 5 × 3 grid with 10 paylines and a single dual-purpose book symbol | Limits feature variety to one mechanic, which some players find repetitive over long sessions |
| Retrigger potential | Allows uncapped retriggers during free spins, extending the bonus round indefinitely | Retriggers depend on scatter frequency, making extended runs rare despite being uncapped |
| Genre variety | Spans Egyptian, Norse, Greek, pirate, and fantasy themes while preserving consistent core mechanics | Repetitive mechanic across themes makes many titles feel structurally identical despite visual differences |
| Legacy trust | Draws on 20 years of player familiarity since Book of Ra established the format in 2005 | Older titles carry lower RTPs (92%–95%) compared to modern slots averaging 96%+ |
Tips for Playing ‘Book of’ Slots
Six tips help navigate the high-volatility profile that defines ‘Book of’ gameplay.
- Verify the RTP before selecting a title. ‘Book of’ RTPs range widely. Book of 99 offers 99.00%. Book of Dead offers 96.21%. Book of Ra Deluxe offers 95.10%. Book of Atem WowPot sits at 92.02% due to jackpot contributions. The difference compounds over hundreds of spins.
- Activate all paylines before spinning. Most ‘Book of’ slots let players deactivate individual paylines. Playing fewer than 10 paylines reduces the number of ways expanded symbols can pay during free spins. Activate all 10 lines to maximize expanding symbol value.
- Budget for the gap between triggers. Free spins trigger approximately once every 100 to 150 base game spins. A $50 bankroll at $0.10 per spin covers approximately 500 spins, providing 3 to 5 expected bonus triggers.
- Evaluate the expanding symbol carefully. The randomly selected symbol determines the bonus round's payout ceiling. Higher-paying symbols (explorers, pharaohs, gods) produce the largest wins when expanded. Lower-paying symbols (card royals) produce smaller returns even when fully expanded.
- Compare ‘Book of’ innovations across providers. Newer releases add meaningful variations: Book of 99 adds wild collection, Book of Shadows adds expandable rows, Book of Inferno adds symbol upgrades, Book of Tut Megaways adds variable reel sizes. Each variation changes the payout behavior.
- Approach the gamble feature with discipline. Many ‘Book of’ slots include a red/black gamble after wins. A correct guess doubles the payout. An incorrect guess forfeits it entirely. Set a strict threshold (never gamble wins above a certain amount) before the session begins.
Summary
‘Book of’ is the slot subgenre that turns free spins into a high-impact event through randomly selected expanding symbols that stretch across entire reels and pay on all paylines simultaneously. The format rewards patience: base game returns are modest, and the largest wins arrive during bonus rounds that trigger infrequently.
Begin with Book of Dead from Play'n GO for the most balanced entry point (96.21% RTP, 5,000x max win) or Book of 99 from Relax Gaming for the highest RTP in the subgenre (99.00%). Both games showcase why the Book of formula has sustained player interest across 2 decades and hundreds of titles.
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FAQ
What are ‘Book of’ slots?
‘Book of’ slots are a subgenre defined by a book symbol that acts as both wild and scatter. Landing 3 or more books triggers free spins with a randomly selected expanding symbol that stretches across entire reels to produce the largest payouts.
How do ‘Book of’ free spins differ from standard free spins?
‘Book of’ free spins feature a randomly chosen symbol that expands to cover the entire reels when it forms a win. Expanded symbols pay across all paylines, even on non-adjacent reels. Standard free spins use normal-sized symbols that pay only on adjacent-reel paylines.
Which game started the ‘Book of’ subgenre?
Novomatic's Book of Ra, released in 2005 for land-based casinos, created the subgenre. Novomatic's online division, Greentube, later brought the game to digital platforms. The expanding symbol mechanic introduced in Book of Ra became the template for hundreds of subsequent titles.
What is the best ‘Book of’ slot?
Book of Dead by Play'n GO (96.21% RTP, 5,000x max win) is the most widely played Book of slot online. Book of 99 by Relax Gaming offers the highest RTP at 99.00%. Book of Tut Megaways by Pragmatic Play features the Megaways engine, offering up to 117,649 ways to win.
Are ‘Book of’ slots always Egyptian themed?
No. The original Book of Ra used an Egyptian theme, but modern ‘Book of’ titles cover Norse mythology (Book of Vikings), Greek legends (Book of 99), fantasy (Book of Shadows), and other settings. The ‘Book of’ mechanic adapts to any theme.
Why are ‘Book of’ slots high volatility?
‘Book of’ slots concentrate their largest payouts in the free spins round through expanding symbols. The base game produces modest returns. This payout concentration creates a high-volatility profile where most session value comes from infrequent but impactful bonus rounds.
Can ‘Book of’ free spins retrigger?
Yes. Most ‘Book of’ games retrigger free spins when 3 or more book symbols land during the bonus round. Each retrigger awards an additional 10 free spins with the same expanding symbol. There is typically no cap on the number of retriggers.
What RTP do ‘Book of’ slots have?
‘Book of’ RTPs range widely across titles. Book of 99 has 99.00%. Book of Dead has 96.21%. Book of Vikings has 96.50%. Book of Ra Deluxe has 95.10%. Book of Atem Wow Pot has 92.02%. Always check the specific game's RTP at the chosen casino.
Do ‘Book of’ slots have a gamble feature?
Many ‘Book of’ slots include a red/black gamble option after wins. A correct guess doubles the payout. An incorrect guess forfeits the entire win. The odds are 50/50. The gamble feature does not change the overall RTP.
Are ‘Book of’ slots available in demo mode?
Yes. Most online casinos offer ‘Book of’ titles in free play or demo mode. Demo play allows observation of how frequently free spins are triggered and how the expanding symbol mechanic behaves, without financial risk.
