Book of 99 Slot Review
Relax Gaming’s entry into the crowded “book of” genre comes with an extraordinary proposition: a 99% RTP, one of the highest you’ll find in modern online slots. Most developers stick to 96-96.5% return to player rates, so when a studio commits to 99%, it signals confidence in their mechanics and target audience. Book of 99 marries this exceptional return with Ancient Greek mythology, drawing inspiration from Homer’s Odyssey through its collection meter mechanic. The game appeals specifically to RTP-conscious players and those seeking a fresh take on the familiar book slot formula.
Base Game & Features
Book of 99 operates on a standard 5×3 grid with 10 paylines. The layout is familiar enough for players accustomed to traditional book slots, but the mechanics differentiate it quickly. Symbols include character representations inspired by Greek mythology (higher value) and royal cards (lower value), with the Book symbol serving dual duty as both wild and scatter. This dual functionality proves central to the game’s two distinct bonus paths.
The base game introduces the Book Collection Meter, a mechanic that separates Book of 99 from standard “book of” releases. Every time a Book wild symbol lands on the reels during the base game, it contributes to a collection meter tracking towards 99. Once you accumulate 99 Book symbols, you automatically trigger the bonus round with 10 free spins—offering a guaranteed path to the feature independent of traditional scatter triggers.
Bonus Features & Free Spins
Triggering the bonus round in Book of 99 follows two paths. The traditional route requires landing 3 or more Book scatter symbols anywhere on the reels, awarding 10 free spins immediately. The alternative comes through your collection efforts: accumulate 99 Book wilds in the base game and reach 100% on the meter for an automatic 10 free spins trigger.
Once free spins commence, the Book symbol opens to a random page, revealing which symbol gains expanding abilities for the entire bonus round. This expanding symbol then transforms gameplay fundamentally. If a character symbol is selected, it requires just 2 symbols anywhere to expand across the entire reel. Royal card symbols set a higher threshold, needing 3 symbols anywhere to trigger expansion. When an expanding symbol lands, it fills its entire reel, dramatically increasing win potential across the remaining paylines.
Retrigger mechanics remain active throughout the bonus: landing 3 or more Book symbols during free spins adds another 10 spins to your total, extending win opportunities. This combination of expanding symbols plus retrigger potential creates the conditions for the 12,075x stake maximum win, achieved when the highest value symbol expands on all five reels simultaneously during an extended bonus session with retriggers.
Game Specifications
Game Name: Book of 99
Provider: Relax Gaming
Release Date: 2021
Grid: 5 reels × 3 rows
Paylines: 10
RTP: 99.0%
Volatility: High
Hit Frequency: 29.83% (approximately 1 win per 3.35 spins)
Minimum Bet: €0.10
Maximum Bet: €100
Maximum Win: 12,075x stake
Theme: Ancient Greek Mythology (Homer’s Odyssey)
Our Verdict
Book of 99 delivers a sophisticated blend of mechanics wrapped around an exceptional 99% RTP. The collection meter mechanic introduces genuine innovation within the book slot category, providing an alternative path to bonus features that sets this title apart from standard “book of” releases. For players prioritising return to player rates, the 99% RTP provides substantial value over extended play sessions, allowing more spins for equivalent spend.
However, the high volatility nature of the game ensures significant bankroll swings despite the generous RTP. You’ll experience extended periods without meaningful wins, a characteristic reinforced by the 29.83% hit frequency. The collection meter itself can prove frustrating during dry spells, particularly when you’re chasing that final stretch to 99 books without seeing sufficient Book symbols. Players expecting frequent bonus triggers or consistent wins won’t find them here—this game rewards patience and capital reserves.
The Ancient Greek mythology theme carries genuine visual appeal, with the game presenting as a very good-looking slot that differentiates itself aesthetically from the usual book slot derivatives. Relax Gaming demonstrates clear skill in combining the recognisable book slot appeal with thematic depth and mechanical innovation.
- Overall Verdict: 4.3/5
- Book of 99 represents a solid entry in Relax Gaming’s portfolio, distinguished by an exceptional 99% RTP and the innovative collection meter mechanic. The game is best suited to RTP-conscious players and those seeking variation within the book slot genre. The high volatility and modest hit frequency mean this isn’t a game for casual play—it requires a longer bankroll and realistic expectations about bonus frequency. The collection feature introduces an alternative path to free spins that rewards engaged players, though extended dry spells can feel punishing. If you appreciate Greek mythology theming and prioritise long-term return to player rates, Book of 99 merits serious consideration. For bonus hitters or high-frequency win seekers, you’ll likely find greater satisfaction elsewhere.
Frequently Asked Questions
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What is the RTP of Book of 99?
Book of 99 is a Relax Gaming slot with an RTP of 99.00%, one of the highest return-to-player rates available in modern online slots. Most games typically fall between 96% and 96.5%, making the 99% RTP the standout differentiator that positions this title as exceptionally generous for RTP-conscious players seeking extended play sessions. -
What is the maximum win in Book of 99?
The maximum win is 12,075x your stake, achieved during the bonus round when the highest value symbol expands on all 5 reels simultaneously. This max win potential is above average even for high volatility games, occurring through the combination of expanding symbol mechanics and free spin retriggers. -
Is Book of 99 a high volatility slot?
Yes, Book of 99 is classified as a high volatility slot. The high volatility designation means players experience larger fluctuations in bankroll swings despite the generous 99% RTP. Despite the exceptional return rate, the game delivers a hit frequency of only 29.83%, resulting in longer periods without significant wins between bonus features. -
How do you trigger free spins in Book of 99?
There are two ways to trigger free spins: (1) Landing 3 or more Book symbols anywhere on the reels awards 10 free spins immediately, or (2) Collecting 99 book wild symbols in the base game fills the collection meter and triggers 10 free spins automatically. Once a mythological character symbol is revealed, it gains expanding abilities throughout the bonus round, filling entire reels for maximum win potential. -
What are the expanding symbols in Book of 99?
The Book symbol opens to reveal which symbol becomes the special expanding symbol during free spins. If a character symbol is chosen, it requires only 2 symbols anywhere on a reel to expand and fill the entire reel. Royal card symbols require a higher threshold of 3 symbols anywhere to trigger expansion. When an expanding symbol lands, it covers the full reel height, dramatically increasing win combinations. -
Can you retrigger free spins in Book of 99?
Yes, you can absolutely retrigger the bonus feature by landing 3 or more Book scatter symbols during the free spins round. When 3 or more Book symbols land during free spins, an additional 10 free spins are added to your total, extending your bonus session and dramatically increasing your win potential. -
What is the hit frequency of Book of 99?
The hit frequency of Book of 99 is 29.83%, meaning approximately 30% of spins result in winning combinations. This translates to roughly 1 winning spin per 3.35 spins. For a high volatility slot, this hit frequency is considered moderate, contributing to the extended dry spells players may experience despite the generous 99% RTP. -
What is the Book Collection Meter in Book of 99?
The Book Collection Meter is a unique feature where you collect Book wild symbols during base gameplay. Collecting 99 book wild symbols fills the collection meter and automatically awards 10 free spins, providing an alternative bonus trigger to landing 3+ scatter symbols. This meter-based mechanic is inspired by Homer’s Odyssey narrative and offers engaged players a guaranteed path to the bonus round through active collection during extended play sessions.
