Book of Monsters (Pragmatic Play) Slot Review

Book of Monsters: Slot Overview 

Don’t let the title fool you — while it might conjure up images of ancient tomes and sinister incantations à la Book of Dead, Book of Monsters by Pragmatic Play is anything but dark and brooding. Released on March 27, 2025, this is a high-volatility grid slot that trades Egyptian tombs for toothy, grinning creatures, and delivers playful, chaotic energy over a 7×7 cluster pays setup. 

Instead of triggering expanding symbols in the classic “book” format, this game features a unique bonus mechanic centered around a special Fat symbol, which grows in size over the course of the free spins round. With the potential to hit up to 5,000x your stake, an RTP of 96.5%, and a hit frequency of 1 in 4.31, Book of Monsters offers players a quirky alternative to the usual “Book of” formula. 

So if you’re looking for a slot that’s more Reacoonz meets Fat Rabbit than Raiders of the Lost Reel, this bright and bouncy title might just be your next monster crush.

Design and Graphics 

Book of Monsters is an explosion of color, charm, and tongue-in-cheek weirdness. Rather than terrifying beasts, the grid is populated by cheeky, cartoonish monsters with glowing eyes, wide grins, and bright colors — purple, green, and red being the standout hues. These little critters look like they’d rather be throwing a party than haunting your nightmares. The game’s background is set in a dimly lit monster cave filled with bubbling cauldrons and floating orbs, while the reels are framed by animated fog and swirling magical energy. During free spins, the lighting shifts from cool blue to orange, visually signaling the increased volatility and excitement. 

The titular Book of Monsters is a grinning, furry character in itself — it hovers beside the reels, flapping open during bonus triggers and gamble opportunities. The overall vibe is a quirky mash-up of Monsters Inc. and Alice in Wonderland, with a healthy dose of psychedelic charm.

Gameplay Mechanics 

The game is built around a 7×7 cluster pays grid, where wins occur when five or more matching symbols connect horizontally or vertically. There are no traditional paylines — instead, it uses a tumble mechanic that removes winning symbols and drops new ones into place, allowing for chain reactions and multiple wins in a single spin. 

Key mechanics include: 

• High volatility math model 

• Tumbles after every win 

• Fat symbols that grow progressively during the bonus game 

• No wilds in the base game 

• Gamble feature for both free spins and bonus enhancements 

Unlike many cluster slots, Book of Monsters doesn’t use sticky wilds, multipliers, or modifiers during the base game — keeping the action simple and building toward the bonus round.

Sound and Music 

The soundtrack matches the game’s zany aesthetic perfectly. A mischievous, magical tune bubbles in the background during base play, with light plucks, sparkles, and monster giggles peppering each spin. It’s upbeat and energetic, helping to create a lighthearted tone even when the wins are slow to come. 

When the bonus round triggers, the atmosphere shifts — the music becomes more intense, sound effects ramp up, and the fat symbol grows in both size and sonic presence. There’s also some tension-building sound design during the gamble feature, where each flip of the book can lead to triumph or an abrupt “The End.”

Bonus Features

Free Spins Trigger 

You’ll need to land 4, 5, 6, or 7 scatter symbols to unlock 5, 6, 7, or 8 free spins, respectively. If the Ante Bet is active (doubling the stake), you can trigger the feature with just 3 scatters, making it 7x more likely to hit. You also have the option to buy the bonus for 100x your stake. Gamble Options Before the round begins, you’re offered a gamble: 

• Gamble for more free spins 

• Gamble for a better Fat symbol 

• Or Collect and play the round as is 

It’s a neat twist, adding strategy and tension right before the most volatile part of the game. 

If you gamble and the book reveals “The End,” you lose the round entirely — so tread carefully! 

Fat Symbol Mechanic 

Once in free spins, a Fat symbol is randomly selected from regular pay symbols. At the start, it appears as a 1×1 cluster and moves to a new location on each spin. 

As you land more of this symbol, it gets collected and stored in a meter. Reaching certain thresholds increases the size of the Fat symbol: 

• 30 collected = 2×2 

• 27 more = 3×3 

• 24 more = 4×4 

• 20 more = 5×5 

• 16 more = 6×6 

• 12 more = 7×7 

Each upgrade also grants 1-3 additional free spins, making it possible to stretch the bonus round for an extended monster feast. 

It’s a rewarding mechanic that gives you a tangible sense of progression and elevates the bonus round far above the base gameplay.

Betting Options and Payouts 

• Min bet: €0.20 

• Max bet: €480 

• RTP: 96.5% 

• Volatility: High 

• Hit frequency: 1 in 4.31 spins 

• Free spins frequency: 1 in 291.02 spins 

• Max win: 5,000x your stake 

• Max win hit rate: 1 in 547,945 

Payout Potential 

Cluster wins can range from 0.2x to 2x for 5-symbol clusters, up to: 

• 100x to 5,000x for a 49-symbol cluster (7×7 full grid) of high-paying monsters. 

With no wilds or base game multipliers, the real money is in the bonus round — particularly if you upgrade your Fat symbol to the 7×7 size and it lands centrally.

Conclusion 

Book of Monsters is a wonderfully strange and visually delightful take on the “Book of” genre, blending familiar bonus triggers with inventive new mechanics. Instead of ancient relics and expanding symbols, you get bouncing, grinning beasts and a progressive Fat symbol mechanic that genuinely adds excitement to the free spins round. 

The base game is admittedly a bit flat, lacking any wilds or modifiers, which makes it feel like a slow build-up to the main event. However, the bonus round more than makes up for it, especially when the gamble feature and Fat symbol growth mechanics start kicking in. 

That said, the 5,000x win cap might feel modest compared to some newer slots, and some players may miss the absence of multipliers or more complex base features. But for those seeking a fresh twist on familiar territory — and a dose of cartoon chaos — this slot delivers.