Book of 99 (Relax Gaming) review: a flat 99% with a 12,075x ceiling
Why this slot is genuinely unusual
Relax Gaming built Book of 99 as a direct answer to a question high-RTP hunters have asked for years: can a slot pay 99% without a catch and still offer a life-changing ceiling? The answer here is yes. The 1% house edge applies flat across all bet sizes, so a £0.10 spin and a £100 spin face the same long-run return. That alone separates it from almost every other "99%" title, most of which either ramp RTP with stake or sit on a tiny max win to compensate.
The trade-off Relax made is volatility. To fund both a 99% return and a 12,075x ceiling, the maths has to be high-variance: small wins are scarce, and the bulk of the return is concentrated in the expanding-symbol free spins. So while the headline is reassuring, the session-to-session experience can be punishing. This is not a low-risk grinder despite the friendly RTP — a distinction we think most listings blur.
Features and theme
The dressing is familiar: an Egyptian "book" slot in the lineage of Book of Ra and Book of Dead, with the book acting as both scatter and wild. Land three to trigger free spins, where a single expanding symbol is chosen and can fill reels for the big hits. A bonus meter adds a layer of progression. There is no feature-buy, so the experience is identical for UK players and everyone else — and there are no bonus-buy RTP caveats to worry about.
What we like — and don't
Strengths
- A true 99.00% RTP at any stake — no mode or coin-bet requirement
- 12,075x max win is huge for a 99% slot
- Fixed RTP: the same value at every licensed casino
- No feature-buy, so no GB restrictions to navigate
- Clean, well-understood 'book' mechanic
Weaknesses
- High volatility means long, dry stretches
- Not the low-risk bankroll-preserver the RTP implies
- Theme is deliberately derivative
- Big wins depend almost entirely on the free-spins symbol
Verdict
Skip if: you need frequent small wins or a smooth ride to clear a bonus — the high volatility undercuts that.
Book of 99 is our pick for anyone who wants the 99% headline to mean exactly what it says. The fixed RTP and absence of a coin-bet trick make it the cleanest near-zero-edge slot in the lobby, and the 12,075x ceiling is a genuine bonus rather than a consolation. Just go in understanding the variance: a 1% edge over millions of spins still allows brutal individual sessions.