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Book of 99 is a slot game by Relax Gaming released in 2021. The game uses classic Book-style presentation with ancient artefacts, a mystical book, an adventure theme and a high RTP that became its main distinguishing feature.

The game grid consists of 5 reels and 3 rows with 10 paylines. The theoretical RTP is 99.00%, which is 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 stake.

Game features

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

The main special symbol is the book. It performs two roles: 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 counter reaches 99 collected symbols, the player gains access 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 these symbols appear, they expand and help create additional payouts on active paylines.

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

The Bonus Meter gives the game a longer-term objective. Even if the bonus is not triggered immediately through 3 Scatters, every collected Wild brings the player closer to the next Free Spins round. 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, a book, card symbols and special bonus icons. Book of 99 belongs to the following categories: Egyptian slots, Book slots and video slots.

The visual style remains clear and traditional: a 5×3 grid, 10 paylines, large symbols and a familiar bonus structure. The main focus is not on complex mini-games but on the high RTP, collecting books and free spins with an expanding symbol.

Popularity among players

Book of 99 is popular among 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, 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.