Free slot: Book of Monsters

Book of Monsters Slot Overview

Step into a world of quirky creatures in Book of Monsters, a slot machine offering wins up to 5,000x your stake. This game blends playful visuals with a cluster pays mechanic and progressive free spins to give you a thrilling experience. 

Book of Monsters is a perfect pick for players who love taking huge risks thanks to its high volatility and very high maximum bet limit. At the same time, casual players can enjoy the fun due to the solid RTP, if they stick to low betting limits. 

Continue reading this review to see what the cheeky monsters have in store for you.

Basic Information 

Released in March 2025 by Pragmatic Play, this slot features 7 reels and 7 rows. It has a clean and responsive design, which makes it easy to play on all devices. 

The minimum bet is €0.20, which is convenient for most casual players. High rollers can also enjoy the thrill of huge risks with up to €480 wager per spin.

Theme and Graphics

This is not a slot of scary or dark monsters; rather, it feels more lighthearted. It plays out in a glowing cave, lit up by eerie blue light and swirling mist. 

On the reels, you’ll see the goofy-looking monsters in different colours, each with silly expressions. In the background, there are ghostly figures peeking through the darkness. 

On the right-hand side, you’ll see a book hanging with a big monster on its cover. It flips open randomly to pick a big Monster, and also when the free spins bonus is triggered. 

Cartoonish music plays in the background, keeping the mood lively and fun as you spin.

RTP and Volatility

Book of Monsters has a decent 96.50% RTP in the regular game, and even with the Ante Bet and Buy Free Spins feature. Theoretically, you should get back €9,650 from every €10,000 wagered over time. 

The volatility is high, so winning clusters form less often on average, but there are more chances to hit big wins. 

Symbols and Paytable 

The high-paying symbols in the slot are three monsters of colours red, green, and purple. Covering the whole grid with red monsters will pay you 5,000x your stake, which is the highest prize in the game.

On the lower end, you have card royals A, K, Q, and J. Symbol J is the least valuable symbol here, and it awards 0.20x for five in a cluster.

How to Play the Slot

To play Book of Monsters, open the game, adjust your stake, and click the spin button. The – and + buttons flanking the spin tab are for changing your bets. 

Game Mechanics

This game uses the cluster pays mechanic, which means you just need at least 5 symbols to connect horizontally or vertically to get a win. There are also payouts for filling the whole 7x7 grid with matching symbols. 

You can set up Autoplay for up to 1000 rounds. There’s also an option to increase the speed of your spins: Turbo Mode.

Feature Symbols Explained

Below, we explain the special symbols to look out for. 

• Bonus Symbol: The BONUS symbol triggers the free spins game with the right combo. It also pays from 2x to 100x your stake for clusters of 3 to 7 symbols.

• FAT Symbol: This is a randomly selected standard symbol that appears in sizes of 2x2 to 7x7. 

Book of Monsters Features and Bonuses

There are just two simple features in the game, but they come with potential for good rewards. We’ve explained them below. 

FAT Symbols 

During the base game, the book by the side of the grid will randomly select a symbol.

This symbol will be upgraded to a random size from 2x2 to 7x7, increasing your chances of making a winning cluster.

Progressive Free Spins

Landing 4, 5, 6, or 7 bonus symbols will trigger 5, 6, 7, or 8 free spins, respectively. When the Ante Bet is active, landing 3 bonus symbols will trigger 3 free spins. 

Before the spins begin, a random symbol is selected as the FAT symbol. After that, you’ll get the chance to gamble and increase the number of spins and change your FAT symbol to a higher value icon.

During the free spins, the FAT symbol starts at the 1x1 size and is always present on the grid, moving to random positions on each spin. 

Every time matching symbols with the FAT symbol land, they’re collected by a meter. The symbols collected determine if you progress to the next level of the free spins. 

For each new level you reach, you get between 1 to 3 additional spins, and your FAT symbol increases in size. The table below shows how many symbols you need to collect and the symbol size on each level. 

Play Options

This title can be played at the numerous sites offering games from Pragmatic Play. You can find them in our list of recommended online casinos or tap the “Play for real” button to be directed to a suitable platform. You can also play for free here. 

At first, the game felt flat for us due to the lack of cascading reels, which we expected from a 7x7 slot. However, the occasional mega symbols awarded big wins and made the game interesting. The progressive free spins with the growing FAT symbol also added more fun.

Play for Real Money or Try the Demo

We recommend trying the demo of the game before playing for real money. This version allows you to enjoy the game for fun without risking anything. It can help you experience the features and also plan how to bet properly when you play for real money. 

If you can’t wait to start grasping at the 5,000x stake prize, then you should play for real money. However, you must play carefully as there are chances of losing money. Pick one of the reputable casinos listed on our platform and register there to play. 

Demo Features and Mobile Compatibility

When you launch the demo, you’ll find up to €100,000 fun credits to play for free. The features are the same as what you’ll find in the real money version. Their difference lies only in the opportunity to win cash. 

Whether you want to play for fun or for real cash, this slot title is available on smartphones and tablets. We tried it out on various Android and iOS devices and enjoyed our experience. You can play seamlessly on a good mobile browser without downloading an app.

Book of Monsters Compared

There are many other slots that come with quirky monsters and aliens, just like this title. Some of them even feature similar bonuses like giant symbols. We highlighted the top options below. 

Similar Slots You Might Like

• Monster Superlanche: Created by Pragmatic Play, this 6x5 grid slot uses an Anywhere Pays mechanic. It offers tumbling reels with multipliers and free spins. The RTP is 96.03%, the volatility is high, and the maximum win is 5,000x stake. 

• Reactoonz: Reactoonz by Play’n GO is a quirky, 7x7 grid slot that uses the cluster pays mechanic. It offers cascading reels and more. It has a 96.51% RTP, high volatility, and a 4,570x stake maximum payout. Reactoonz 2 was released as a sequel. 

• CritterPop: Designed by AvatarUX, this is a 5x3 grid slot that can expand up to 65,536 winning ways. The game offers special symbols, multipliers, and free spins. Its RTP is 96%, volatility is high, and the maximum payout is 20,000x stake.

Summary & Final Verdict

Book of Monsters is another top-notch, whimsical slot with a monster theme. Its lighthearted visuals and sound effects keep things lively while the FAT symbols and free spins bring in the real fun and rewards. 

Though the slot has high volatility, its 96.50% RTP is quite solid. With good bankroll management, you can play enough rounds and may be lucky to hit the 5,000x max win. It’s sure worth a try if you love quirky slots.