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Relax Gaming

Book of 99 by Relax Gaming — RTP 99.00%

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Book of 99 Overview

Book of 99 by Relax Gaming returns 99.00% over its lifetime, putting it in the top tier of online slots. Below you will find how it compares to the rest of Relax Gaming's catalogue, and — where we have tracked enough real bets — how often it actually pays.

About Relax Gaming: Relax Gaming offers a diverse portfolio of slots alongside their aggregation platform. Their in-house titles are known for creative features and balanced volatility profiles.

How Often Book of 99 Is Played

Measured

We recorded 595 spins on Book of 99 from 32 different players between Aug 15 and Sep 14, 2026. That makes it the #350 most played game of the 2,205 we saw in that period — ahead of 84% of them.

595 spinsMost played game: 61,797
Spins recorded
595
Players seen
32
Rank of 2,205
#350

Counted from bets that appeared in Duel.com's public live feed, which shows a sample of play rather than every bet placed. It is a fair basis for comparing how often games are played, but not for judging how much they pay out — we publish no payout figures from this source.

RTP Analysis

Book of 99 has a theoretical RTP of 99.00%. This is +3.00pp above the industry average of 96.00%. Compared to other Relax Gaming slots (average 95.96% across 142 titles), it offers a +3.04pp higher return.

vs Industry Avg
+3.00pp
Relax Gaming Avg
95.96%
vs Relax Gaming Avg
+3.04pp

Game Details

Book Collection TriggerFree SpinsExpanding SymbolsRetrigger
Mechanic: paylineTheme: Ancient GreeceBooksMythology

Data by slot.report & SlotsLaunch

RTP Verdict

Generous Maths

Book of 99 keeps 99.00% on the table over the long run — about 3.00 more per $100 wagered than the typical slot. That edge is small per spin and compounds only over very long play, but unlike anything you can read off a single session, it is real and it does not change.

Frequently Asked Questions

What is the RTP of Book of 99?
Book of 99 by Relax Gaming has a theoretical RTP of 99.00%, which is above average for online slots. This is the figure the game's maths returns over its full lifetime, certified by an independent testing lab — not a reading from recent play.
Is Book of 99 paying well right now?
There is no honest way to answer that, and we would rather say so than invent a number. Reading a single slot's actual return to within a percent takes tens of millions of spins on that one game, because one large hit outweighs weeks of ordinary play. Any site quoting you a slot's "RTP today" is quoting noise. What we do publish, where our tracker has recorded enough real bets, is how often the game pays at all — a figure that settles far faster and is shown on this page with its confidence interval.
Do slots go hot or cold?
Not in any way you can use. We tested our own recorded bet series for the serial correlation a genuine streak would leave behind, using Ljung-Box autocorrelation tests, and found none — the results are indistinguishable from independent draws, which is exactly what a certified random number generator is meant to produce. A game that has paid well recently is no more and no less likely to pay on the next spin.
Who made Book of 99 and where can I play it?
Book of 99 is developed by Relax Gaming. You can play it on Duel.com and other crypto casinos that carry Relax Gaming titles. The game's maths is identical wherever you play it — operators cannot change a certified RTP, though some games ship in several certified versions and an operator may choose which to run.
How does Book of 99's RTP compare to other Relax Gaming slots?
Book of 99 returns 99.00%, which is above average for the industry (average 96.00%). The spread within a single studio is usually wider than the gap between studios, so it is worth comparing title by title — our Relax Gaming page lists every one we hold with its published return.
What does the generous maths verdict mean for Book of 99?
Book of 99 keeps 99.00% on the table over the long run — about 3.00 more per $100 wagered than the typical slot. That edge is small per spin and compounds only over very long play, but unlike anything you can read off a single session, it is real and it does not change.
Is Book of 99 worth playing?
Book of 99 has a theoretical RTP of 99.00%, which puts it among the better-value slots available — the house keeps less of your stake here than on most titles. That is a genuine advantage, though a modest one: it shows up over tens of thousands of spins, not over an evening. Everything else about whether to play it comes down to whether you enjoy the game.

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Disclaimer: RTP data is collected from third-party sources and may fluctuate. Past RTP performance does not guarantee future results. Gambling involves risk. 18+ only. Gamble responsibly.