Book of 99 — slot review

Book of 99 is a slot by Relax Gaming (released 2021) with an RTP of 99%, high volatility. Theme: ancient Greece, the book.

RTP 99%High volatility5x3

Free demo

Free, virtual chips only — no sign-up

Demo mode uses a virtual balance and pays no real winnings. It is meant for getting familiar with the game.

Specifications

Provider	Relax Gaming
Release year	2021
RTP	99%
Volatility	High volatility
Reels	5x3
Paylines	10 paylines
Theme	ancient Greece, the book
Mechanics	expanding symbols, free spins, symbol collection

Why the RTP at a casino may differ

Providers ship the same game in several return configurations, and each casino picks which version it runs. Across the market the spread typically runs 2–8 percentage points below the headline figure. The number here is the provider specification — the version actually running is shown inside the game, in its rules screen.

Book of 99 review

Book of 99 made headlines across the market with a single number — a 99% RTP, an almost unheard-of return for a video slot. Structurally it's a classic "book": a 5x3 grid, ten lines, a book scatter and free spins with an expanding special symbol in the Book of Ra mould. But Relax added a twist: collect 99 of the hero's symbols and you're granted a bonus retrigger with a guaranteed premium expanding symbol. Thanks to that razor-thin house edge, the slot is adored by strategic players and bonus-clearing grinders wherever the terms allow it. For anyone who prizes the maths over the graphics, this is essential viewing.