Book of Fusion Slot by Light & Wonder

Book of Fusion drops you into a steampunk laboratory where alchemy and electricity crash together. Light & Wonder built this 2022 release on the NOVA Core v4.0.2 engine (the old NextGen pure pipeline), and the visual identity is immediate: a 5x3 reel set framed in heavy copper and brass, teal-tinted reels behind riveted bronze pipes, bubbling alchemy flasks at the right edge, and the BOOK OF FUSION title rendered in chrome pink-and-blue lettering with the bonus book glowing underneath. Symbols mix industrial machinery (a Tesla-coil bulb, an orange-red electromagnet, a voltage meter, a valve regulator) with the Mad Scientist himself as the Wild.

The math is classic high-volatility Book of territory. RTP sits at 96.00%, you get 10 fixed paylines across the 5x3 grid, and bets run from $0.01 up to $35.00 with a $2.00 default. The Mad Scientist Wild does double duty: it substitutes for regular symbols in base-game line wins and also pays as a scatter, so you can collect a Wild payout without it landing on adjacent reels. One caveat worth flagging upfront: Light & Wonder hasn't published a max-win multiplier for this build, so the ceiling is genuinely opaque until the bonus pops.

The headline reason to play sits inside the Free Spins bonus. Land 3 or more purple-and-gold Book of Fusion scatters anywhere on the reels and you get 10 spins. Here's the twist that puts this in the Book of Ra family of expanding-symbol slots: at the start of the round, the game randomly picks TWO Special Symbols (not one, like the original Book of Ra). During the bonus, those specials grow to fill entire reels and pay anywhere across the 5 reels, no adjacency required.

Retriggers stack. Land 3 or more books again during free spins and you bag another 10 spins plus two more Special Symbols added to the active pool. Keep retriggering and the pool keeps growing until eventually all 10 base symbols can expand. There's also a Buy Pass option (a direct bonus purchase) that guarantees a spin position landing at least 3 bonus books, with cost and Buy Pass RTP shown on the confirmation screen. Availability depends on jurisdiction; UK retail often disables it.

Honest take? The two-Special starting hand is more generous than classic Book of Ra, but with only 10 paylines, even a fully expanded Mad Scientist still needs cooperation from other Special positions to deliver a knockout hit. Where Book of Fusion genuinely shines is the stackable retrigger, if you can chain books, the entire symbol pool can eventually turn into expanding payers. High variance, patient bankroll required, but the bonus ceiling is properly exciting when it cooperates.