Book of 99 delivers a groundbreaking 99.00% theoretical return to player, substantially higher than the industry standard of 94-96%. This means that for every hundred units wagered, the game theoretically returns ninety-nine units over the long term, giving players exceptional value and extended gameplay sessions on the ancient Greek reels.
Every wild Book symbol that lands during base game spins adds to your collection meter. Once you gather all ninety-nine golden books, you trigger free spins at the weighted average bet of your collection journey.
The ornate golden book serves dual functions: it substitutes for all regular symbols to complete winning combinations across the ten paylines, and each appearance in the base game increments your collection meter.
Dual FunctionTrigger ten free spins either by landing three or more Book wilds in a single spin, or by completing the collection of ninety-nine wilds. One of the nine regular symbols is randomly chosen as a special expanding symbol for the entire feature.
10 Spins AwardedDuring free spins, if two high-value symbols or three low-value symbols of the chosen special type land anywhere on the reels, they expand to fill entire columns and pay on all ten lines regardless of their horizontal position.
High Value: 2+ Symbols Low Value: 3+ SymbolsBook of 99 stands apart in the crowded Greek mythology slot market through its innovative collection mechanic and industry-leading return to player. The journey to ninety-nine wilds creates genuine anticipation across sessions, while the dual trigger system for free spins ensures frequent feature activation. The expanding symbol mechanic during free spins can deliver substantial wins when high-value characters fill multiple reels.
Use the minus and plus buttons flanking the bet display to select your wager per spin. The game always plays all ten paylines.
Press the large circular spin button in the centre of the control bar to set the five reels in motion across three rows.
Win by landing three or more matching symbols on any of the ten paylines, evaluated from left to right starting at the leftmost reel.
Each golden Book wild that appears increments the collection meter visible on the left side. Track your progress toward the ninety-nine target.
Activate the bonus by landing three or more Book wilds in one spin, or by filling the collection meter to ninety-nine.
During ten free spins, the randomly selected special symbol expands across full reels when sufficient instances appear, paying on all lines.
The 99.00% return to player rate is exceptionally high for online slots. Most games range from 94% to 96%, meaning Book of 99 theoretically returns three to five percentage points more to players over the long term. This translates to extended gameplay and better value from your bankroll.
Every time a golden Book wild symbol lands anywhere on the five-by-three grid during base game spins, it adds one unit to your collection meter displayed on the left side of the screen. The meter tracks from zero to ninety-nine. When you reach ninety-nine collected wilds, you automatically trigger ten free spins. The collection persists across sessions until triggered.
First, you can trigger ten free spins immediately by landing three or more Book wild symbols anywhere on the reels in a single spin. Second, you activate the feature by collecting ninety-nine Book wilds over time through the collection meter. Both methods award ten free spins with a randomly selected expanding symbol.
At the start of free spins, one of the nine regular symbols is randomly chosen as the special expanding symbol. During each free spin, if two or more high-value expanding symbols appear anywhere (or three or more for low-value symbols), they expand to cover their entire reels. The expanded symbols then pay on all ten paylines regardless of their position, not requiring left-to-right adjacency.
Yes. If three or more Book wild symbols land anywhere during your free spins feature, you receive an additional ten free spins. The same expanding symbol continues throughout the retriggered spins. You can retrigger multiple times within the same feature.
When free spins are triggered by reaching ninety-nine collected wilds, the bet size used is the weighted average of all bet amounts you used while collecting those wilds. This average is rounded to the nearest valid bet multiple using stochastic rounding. Free spins triggered by landing three or more wilds in one spin use that triggering spin's bet amount.
Relax Gaming is a B2B supplier delivering high-quality online casino content to operators globally. Established in 2010, the Malta-based studio has built a reputation for innovative mechanics and player-focused design.
Book of 99 represents their commitment to transparency and value, featuring certified random number generation and the verified 99.00% return to player rate. The game is licensed and regulated for fair play across multiple jurisdictions.
Book of 99 is a game of chance. While the 99% RTP is higher than most slots, it represents long-term theoretical return and does not guarantee individual session outcomes. Set deposit limits, take regular breaks, and never wager more than you can afford to lose. If you feel your gambling is becoming problematic, seek support from organisations like GamCare or BeGambleAware. Players must be eighteen years or older.
