Explained: Book Of Slots

We speak to ESA Gaming’s Head of Game Production, Josefin Uppeke to get the lowdown on Book Of slots and what makes them so popular with players

Book Of slots are hugely popular with players in the UK. These games feature a Book symbol that acts in two ways – the first as a Wild and the second as a Scatter, triggering Free Spins and other bonuses. 

When we think of the best Book Of slots, we often think of Rich Wilde and the Book of Dead from Play’n GO, but given the category’s popularity, more studios are now launching slots using the Book Of format. 

This includes ESA Gaming which recently rolled out Book of Rrrum, its first title in the category. It takes the pirate theme, with players being players finding themselves at the helm of a mighty ship as it sails across the rough seas in search of treasure and big wins. 

To learn more about the game, and what makes Book Of slots so popular with players, we sat down with Josefin Uppeke, Head of Game Production at ESA Gaming. 

First things first, what do we mean by ‘Book Of’ slots?

‘Book Of’ slots refer to a unique category of slot games characterised by the inclusion of a special book symbol that serves a dual purpose, acting both as a Wild, substituting for other symbols to form winning combinations, and as a Scatter, triggering Free Spins or bonus rounds. This hybrid mechanic adds a layer of excitement to the gameplay, offering simplicity yet delivering high-stakes thrills.

Whilst traditional ‘Book Of’ slots typically feature a 5×3 grid layout (5 reels, 3 rows) with fixed paylines, modern innovations have occasionally deviated from this setup, introducing new grid structures or different paylines to refresh the gameplay whilst staying true to the genre’s core appeal.

Can ‘Book Of’ slots be based on different themes and characters?

Yes, and this is part of their charm! While many early entries in the genre were inspired by Egyptian themes, today’s ‘Book Of’ slots span a variety of settings, from mythology to fantasy, and now, with Book of Rrrum, the high seas with a pirate twist.

What makes ‘Book Of’ slots so popular with players?

Their popularity stems from a perfect balance of simplicity and excitement. Players know what they’re getting: a classic slot experience with a signature twist. The Free Spins with expanding symbols create thrilling moments where even a single spin can lead to substantial payouts. The high-volatility nature of the games adds an adrenaline rush, while the variety of themes keeps players engaged over time. There’s a reason why this genre continues to be a mainstay in the industry – it just resonates with players in a way that few others do.

You recently launched your first ‘Book Of’ slot – Book Of Rrrum. Tell us more about the game.

Book Of Rrrum marks our first venture into the ‘Book Of’ genre, and we couldn’t be more excited about it. It stays true to the core mechanics players love, with 10 paylines and the classic book mechanic, but we’ve added our own unique twists. The Cascading Wins and Multipliers create a dynamic experience that keeps every spin engaging, whilst also offering two Free Spin modes where the Super Free Spins are more volatile and have bigger increasing multipliers.

The Boost feature is a game-changer, giving players a chance to trigger the book mechanic randomly during the base game and also a 50/50 chance to trigger any of the two Free Spin modes. Then there’s the pirate theme, which we’ve brought to life with vibrant visuals and immersive sound effects. All these elements come together to create a slot that feels both familiar and fresh.

What makes it stand out from other ‘Book Of’ slots?

What sets Book Of Rrrum apart is how it takes the proven ‘Book Of’ formula and elevates it. The Cascading Wins mechanic adds a layer of unpredictability and excitement, as every win creates a chance for more symbols to drop and increases the Multiplier that sticks to the very end of Free Spins.

The Boost feature is another standout, as it gives players an added sense of anticipation, knowing that the book mechanic can activate at any moment during the base game. And then there’s the Super Free Spins mode, where enhanced Multipliers make the potential rewards even more thrilling. All of this is wrapped up in a vibrant pirate adventure that immerses players in a world of treasure maps, hidden loot, and, of course, plenty of Rrrum.

If the player hasn’t tried a ‘Book Of’ slot before, why should they take one for a spin?

If you’ve never played a ‘Book Of’ slot, Book of Rrrum is the perfect introduction. It combines everything that makes the genre exciting—simple mechanics, high volatility, and the chance for significant wins—with unique features that keep it fresh and engaging. Whether you’re a casual player or a seasoned slot fan, these games have something for everyone.