The “Book of”

Slot Mechanic

The “Book of”

Slot Mechanic

Exploring the “Book of” Mechanic in Online Slots

In the world of online slot games, few features have moved the dial on design and gameplay as much as the “Book of” mechanic.

Originating from the renowned slot game “Book of Dead” by Play ‘n Go, this feature has become a staple in the industry, shaping slot design and offering a blend of excitement and anticipation for players worldwide.

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Understanding the “Book of” Slot Mechanic

book of the irish slotThe “Book of” mechanic typically revolves around a special symbol, which is often a mystical book (hence the name of the feature!) This symbol functions both as a Wild and a Scatter, triggering various features within the game. When three or more book symbols land on the reels, it often leads to a free spins round and grants payouts regardless of their position on the screen.

Once the free spins feature triggers, one symbol is chosen at random to become an expanding symbol. When this symbol appears during the free spins, it expands to cover an entire reel, which can lead to some decent wins. The mechanic’s simplicity and potential for significant payouts have made this feature very popular among players.

Riche Wild and the Book of Dead

rich wilde book of dead mechanicLet’s take a close look at Rich Wilde’s most famous game as this will explain the feature perfectly.

Imagine embarking on an adventurous journey with Rich where a magical Expanding Symbol holds the key to your wins. Picture this: when you land three Scatter Symbols on the reels, steel yourself to unlock a treasure trove of ten Free Spins – the gateway to potential big Wins!

Here’s where the excitement kicks in. Before these Free Spins kick in, a regular symbol is handpicked to transform into a Special Expanding Symbol for the entire Free Spins round. It’s like having a secret weapon in your arsenal, poised to expand and cover an entire reel whenever it appears.

If your luck is really in and you land another set of three or more Scatter Symbols during the Free Spins, you will retrigger the Free Spins feature, which nets you another ten free spins to keep the action going.

In a nutshell, it’s all about those Free Spins, the Special Expanding Symbol, and the chance to unlock additional wins along the way.

Games Featuring the “Book of” Mechanic

Many games that use this mechanic, such is its appeal. Besides “Book of Dead,” titles like “Book of Ra” by Novomatic and “Legacy of Dead” by Play ‘n Go are prime examples. Arguably Novomatic’s “Book of Ra” series paved the way for this mechanic’s popularity, with its iconic gameplay and rewarding features, inspiring many other developers.

The mechanic’s success has encouraged other game designers to create their own versions, infusing their unique themes and twists into the gameplay. Titles like “Book of Oz” by Microgaming and “Book of the Irish” by Inspired all showcase the versatility of this mechanic across different themes and designs.

Pros and Cons of the Mechanic

Simplicity: The mechanic’s straightforward gameplay appeals to both seasoned and new players.
High Volatility: It offers the potential for big wins due to the high volatility nature of the mechanic.
Exciting Features: The anticipation of the free spins round and the expanding symbols creates an engaging experience.
Adaptability: Developers can incorporate diverse themes into the mechanic, ensuring a wide range of options for players.

❌ Predictability: Some might find the mechanic’s predictability repetitive after a while on the reels.
High Variance: While it can lead to significant wins, it also means periods of low activity, which may not suit all players.
Saturation: There are quite a few games that have just “jumped on the bandwagon” without bringing anything new to the party.

Prominent Design Studios and Their “Book of” Games

Several of the best casino game development studios have gone all in with the “Book of” mechanic in their titles. Play ‘n Go, the pioneer with “Book of Dead,” continues to innovate within this space. Games Global’s partners such as Triple Edge are also active in this sector, and Pragmatic Play are another developer to watch out for if you like these kinds of games.


The “Book of” mechanic has left an indelible mark on the landscape of online slot gaming. Its blend of simplicity, high volatility, and potential for significant wins has solidified its place as a beloved feature among players.

Despite some drawbacks like predictability and market saturation, the mechanic’s adaptability and the excitement it brings during gameplay continue to make it a feature that players seek out. With its widespread adoption by multiple design studios, the “Book of” mechanic should remain a prominent and enduring mechanic in the world of online slots for the foreseeable future.