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Book of 99 is an online slot from Relax Gaming, released in 2021. The game uses a classic Book-style setting with ancient artefacts, a mystical book, adventure imagery and a high RTP that became the game’s main distinguishing feature.

The game area consists of 5 reels and 3 rows with 10 paylines. The theoretical RTP is 99.00%, noticeably above the average level for online slots. Volatility is high, the betting range is usually listed as 0.10 to 100, and the maximum win reaches 12075x the bet.

Game features

• Wild symbols
• Scatter symbols
• Free Spins
• Expanding Symbols
• Bonus Meter
• Symbol Collection

The main special symbol is the book. It performs two functions: it substitutes for regular symbols as a Wild and triggers free spins as a Scatter. Landing 3 or more Book symbols activates the Free Spins bonus mode.

The game also includes a Wild-symbol collection meter. Every Book/Wild that appears is added to the Bonus Meter. When the meter reaches 99 collected symbols, the player gains entry to the bonus mode even without the standard Scatter combination.

Bonus mechanics

Free Spins are the key feature in Book of 99. At the start of the bonus, one special symbol is selected; during the free spins it can expand on the reels. If enough of that symbol appears, it expands and helps form extra payouts on active paylines.

Expanding Symbols make the bonus mode the main source of larger potential. A particularly strong result is possible when one of the high-paying symbols is chosen as the expanding symbol.

Bonus Meter adds a longer-term objective to the game. Even when the bonus does not trigger immediately through 3 Scatters, every collected Wild brings the player closer to the next Free Spins entry. This makes Book of 99 feel more progressive than many classic Book slots.

Theme and style

The slot uses an adventure style with references to ancient treasures, a mystical book and classic Book of games. The reels feature characters, artefacts, the book, card symbols and special bonus icons. Book of 99 belongs to the categories: Egyptian slots, Book slots, video slots.

The visual design remains familiar and traditional: a 5×3 grid, 10 paylines, large symbols and a recognisable bonus structure. The emphasis is not on complex mini-games but on the high RTP, book collection and Free Spins with an expanding symbol.

Popularity among players

Book of 99 is popular with players from the United Kingdom, Canada, Germany, the Netherlands, Norway, Sweden, Finland, Denmark and New Zealand. It may appeal to users who enjoy Book-style mechanics, a high RTP, free spins and a simple structure without overloaded extra modes.

The slot suits players who prefer high volatility, fixed paylines, a Wild/Scatter book and a bonus round where the main potential comes from expanding symbols.