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Book of 99 — a slot by Relax Gaming, released in 2021. The game uses classic Book-style visuals with ancient artefacts, a mystical book, adventure-themed artwork and a high RTP that became its main 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 bet.

Game features

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

The main special symbol is the book. It has two functions: it substitutes for regular symbols as Wild and triggers Free Spins as Scatter. If 3 or more Book symbols land on the reels, the Free Spins bonus mode is activated.

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 enters 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, a special symbol is selected and can expand on the reels during the free spins. If enough of that symbol appears, it expands and helps create additional payouts on active paylines.

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

Bonus Meter gives the game a longer-term objective. Even if the bonus is not triggered immediately by 3 Scatter symbols, every collected Wild moves 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, a book, card symbols and special bonus icons. Book of 99 falls into the categories: Egyptian slots, Book slots, video slots.

The visual style remains straightforward 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 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. The game may appeal to users who enjoy Book-style mechanics, high RTP, Free Spins and a simple structure without overloaded extra modes.

The slot may suit players who prefer high volatility, fixed paylines, a Wild/Scatter book and a bonus round where the main potential comes from Expanding Symbols.