What Is Book of Monsters?

Book of Monsters breaks from the usual "Book of" template on purpose. Most games in that genre — Book of Dead, Book of Ra, the dozens of clones since — use a book scatter that expands one symbol across a payline grid. This one doesn't have paylines at all. Instead, it's built on a 7x7 cluster-pays grid, where five or more matching symbols connected vertically or horizontally form a win, and the theme leans into cartoon monsters that look more like rejects from an animated kids' show than anything trying to be scary.

Low-paying symbols are the four card suits — jack, queen, king, ace — and above them sit three colored monster characters, purple, green, and red, each worth progressively more. A cluster of five matching symbols pays a modest 0.2x to 2x your stake, but that number scales hard: a full 49-symbol cluster on the highest-paying monster pays out the game's full 5,000x ceiling.

The base game is genuinely sparse in terms of features — there's no tumble mechanic and no wild, so most of what you're doing outside the bonus round is just working toward triggering it. Four or more of the orange alien scatter symbols land the free spins round, with the exact count determining how many spins you start with and a small accompanying payout.

Fat Symbols and How the Free Spins Round Grows

The free spins round is where Book of Monsters earns its "Book of" name — sort of. A magic book above the grid periodically selects a random symbol and turns it "Fat," meaning it starts occupying a larger footprint on the grid, up to the full 7x7 size at its maximum level. The bigger a Fat symbol gets, the more of the grid it can singlehandedly cover, which is what makes cluster sizes — and payouts — snowball as a round progresses.

What sets this game apart is a gamble mechanic that shows up periodically during the bonus: you can choose to gamble for extra free spins or for a bigger Fat symbol, each with a stated success percentage shown on screen, or just collect what you've built so far. It's a genuine risk decision baked into the bonus round itself — pushing your luck can extend a good round significantly, but a failed gamble ends the feature immediately, on the spot.

Ante Bet doubles your stake in exchange for needing only 3 scatters to trigger the round instead of 4, cited as roughly a 7x boost to your odds of hitting it naturally. A Bonus Buy option, where available, jumps straight into free spins for around 100x your stake.

RTP, Volatility and the Gamble Decision

Default RTP is 96.50%, with lower operator configurations of 95.50% and 94.50% also certified — check before you play. Volatility sits at the top of Pragmatic Play's scale, 5 out of 5, and it shows: the bonus round triggers naturally around once every 291 spins on average, which is a long wait without the Ante Bet's boost.

The 5,000x max win requires filling a large portion of the grid with the highest-value monster at its full Fat size — a genuinely rare confluence of events, but one that at least feels earned given how visibly the round builds toward it, rather than arriving out of nowhere. Bets run from around $0.20 up to $240 depending on the operator.

Our Verdict

Book of Monsters is one of the more interesting "Book of" entries precisely because it barely resembles the genre it's named after. The cluster-pays structure on a 7x7 grid plays differently from payline-based book slots, and the in-round gamble decision — extend the feature or bank what you've got — adds a layer of actual choice that most high-volatility slots don't bother with. It's not for players who want steady action; the base game is thin by design, and you're largely spinning to reach the bonus. But once you're there, the format has more going on than its cartoonish presentation suggests.

Where to play it

We recommend Gamdom for playing Book of Monsters with real money: 15% Rakeback for 7 Days.

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