Return to Player
96.5%
Minimum bet
0.20
Slot type
Video Slots
Volatility
High
Reels
7
Progressive jackpot
No
Popularity
Maximum bet
480
Provider
Pragmatic Play
Bonus features
Yes
Paylines
Cluster Pays
Theme
Monsters
Book of Monsters online slot
Pragmatic Play gives the Monsters, Inc. concept another mischievous twist with Book of Monsters. This cluster-pays slot features wide-eyed, toothy creatures in a strange underground world, though they look less fearsome than their reputation suggests. The cavern itself is more ominous, with glowing spectres, drifting fog and a distinctly spooky feel. The result is a playful monster adventure featuring unusual characters, hidden surprises and the possibility of sizeable wins.
Book of Monsters: Key Facts at a Glance
- Book of Monsters has an RTP of 96.50%.
- Winning combinations are determined by a Cluster Pays system.
- Features include Free Spins, Ante Bet and Bonus Buy.
- Each time a special Fat symbol grows, it awards extra spins.
Book of Monsters: Graphics and Sound
Friendly, floating creatures bring Book of Monsters’ unusual world to life, while darker figures lurk at the edges with glowing eyes and menacing grins. A rough stone cavern forms the backdrop, its ancient-looking walls lit by a soft blue glow.
When Free Spins start, the scene shifts to a vivid orange chasm. An enchanted book hovers above a stone plinth on the right of the screen, setting off transformations that could startle the cave’s inhabitants and potentially benefit the player.
Suspenseful drones, chirpy notes and springy vocal effects add energy to each change. Together, these elements create a spooky yet playful atmosphere that keeps the focus on the cave’s hidden mechanics.
Top Casinos for Playing Book of Monsters:
How to Play the Book of Monsters Slot
Book of Monsters is a 7x7 slot set among unruly creatures that struggle to control their growth. To win, connect at least five matching symbols vertically and/or horizontally across adjacent reels to form a cluster.
The main board features two groups of symbols. The lower-paying group comprises the familiar royal card ranks J, Q, K and A. The higher-paying icons show three distinct monsters in purple, green and red.
There are no Wild symbols. Instead, ‘Fat symbols’ may appear at random and cover 3x3, 4x4, 5x5, 6x6 or 7x7 spaces in the base game, potentially boosting a win. Free Spins, Ante Bet and Bonus Buy provide further ways to change up this monster-themed slot.
Trying the Book of Monsters demo
Casino Ideal’s review features the free-play version as a way to explore Book of Monsters’ narrow tunnels and hidden passages. In demo mode, players can check out the mechanics, special symbols and bonus features without wagering money. It can help you decide whether the game suits your tastes before considering real-money play.
Book of Monsters Bonus Features
Book of Monsters keeps its bonus selection focused, with Free Spins providing the main opportunity for an extended round. Here’s a look at the features:
Free Spins Feature: The orange alien acts as a Bonus Scatter in Book of Monsters. Landing 4, 5, 6 or 7 of these symbols triggers Free Spins and awards 5, 6, 7 or 8 free spins, respectively.
Before the feature starts, the game randomly chooses a paying symbol to become the Fat symbol. Players can gamble for a higher-value symbol, risk their spins for extra free spins, or collect the displayed Fat symbol and free spins to start the round.
If a gamble for extra free spins or a more valuable Fat symbol reveals ‘The End’ in the monster book, the bonus ends immediately. A successful gamble can award up to 8 extra free spins and upgrade the Fat symbol to its highest available value.
The free spins round also features a progressive Fat symbol. It begins as a 1x1 icon, moves to a different grid position after each spin and collects qualifying appearances in a meter. Symbols covered by the Fat symbol do not count. Each threshold reached enlarges it; there are six possible sizes:
- Collect 30 to grow the Fat symbol to 2x2.
- Collect 27 more to grow it to 3x3.
- Collect 24 more to grow it to 4x4.
- Collect 20 more to grow it to 5x5.
- Collect 16 more to grow it to 6x6.
- Collect 12 more to grow it to 7x7.
Whenever the Fat symbol grows, the game randomly awards 1, 2 or 3 extra free spins.
Ante Bet: Choose a bet multiplier before the game starts. The selected stake affects the feature rules as follows:
- 40x bet multiplier – The chance of triggering Free Spins is seven times higher. Landing 3, 4, 5, 6 or 7 bonus symbols awards 4, 5, 6, 7 or 8 free spins, respectively.
- 20x bet multiplier – The game uses its standard rules, with no added benefits.
Bonus Buy: Pay 100x the current total bet to enter Free Spins directly from the base game. A purchased triggering spin can randomly land 4, 5, 6 or 7 Bonus symbols.
Book of Monsters Slot Strategies and Tips
These suggestions can help you understand the choices in Book of Monsters and manage your balance:
- Choose your bet multiplier carefully: The 40x bet multiplier increases the stated chance of triggering Free Spins by 7x, but also changes the stake. For a less aggressive approach, try the regular game and read about balanced volatility.
- Weigh up Bonus Buy: If you have sufficient funds and want to skip the base game, you can buy Free Spins for 100x the total bet. The feature can also award more free spins, but consider the price and high variance before buying.
Book of Monsters Technical Details
Pragmatic Play’s Book of Monsters is a high-volatility cluster-pays slot with a 96.5% RTP. Bets range from 0.20 to 240 per spin, and the stated maximum win is up to 5,000x the stake. Its distinctive ‘Fat Symbols’ can grow during free spins, changing the feature’s layout and adding another dimension to the round’s potential outcomes.
Alternatives to the Book of Monsters Slot
If you’re after more monster-themed slots, these titles may also be worth a look:
- Aliens: Aliens is a 96.4% RTP NetEnt slot inspired by the blockbuster film that audiences have come to admire and fear. This five-reel, 15-payline game pairs an intergalactic setting with hostile aliens, bonus rounds and collectible multipliers.
- Immortal Romance: Immortal Romance has a 96.96% RTP and 243 ways to win. It features an unfolding story, detailed visuals and four distinct free spins rounds, and is designed for mobile and desktop play.
Our Verdict
Evan Carrington’s review characterises Book of Monsters as a fairly straightforward slot where a book randomly selects a special symbol before awarding free spins. The chance of losing the entire bonus through a gamble can make the feature feel restrictive. The base game may also seem quiet, and its high volatility might not suit casual players looking for steadier risk. The growing Fat symbol is the game’s standout feature and offers the potential for larger wins, but no result is assured.
Evan Carrington brings more than 12 years of experience in the iGaming industry, with a focus on reviewing online casinos, assessing slot games and examining player safety. Their work covers casino licensing, RTP, volatility, bonus terms and withdrawal policies. Drawing on practical testing and independent research, Evan provides clear, evidence-based reviews to help players understand gambling platforms, their features and possible risks.
