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We spent 100x on a bonus buy and got 7.4x back. That result will not define every session, but it does give a fair sense of the slot’s volatility. Lucky Monaco’s space-themed slot wraps the familiar “Book of” expanding symbol format in a cosmic skin, complete with glowing planets and a pulsing synth soundtrack. The standout feature is the cosmic cube that rolls before Free Spins, assigning both your expanding symbol and a multiplier in one random moment. Up to a 100x multiplier is visible on that cube. The problem is reaching it, and then getting anything meaningful out of it once you do.
Book of the Universe runs its scatter and wild functions through a single symbol. Land three or more anywhere on the reels during regular play and Free Spins trigger automatically. As a wild, it substitutes for every symbol except the expanding symbol during the bonus round. Five wilds across a payline return 250x your bet. The symbol appears on all five reels, giving it decent coverage across the grid.
Free Spins awards 10 spins, but the defining system is what happens before they begin. A cosmic cube animation plays, rolling to assign an expanding symbol and a multiplier value simultaneously. You don’t choose; the game decides. The multiplier range includes values up to 100x, though the actual distribution isn’t disclosed. The expanding symbol then dictates which symbol grows vertically when forming winning combinations during the round. Standard wins calculate first, then expanding symbol wins apply with the multiplier on top.
The expanding symbol doesn’t need adjacent reels to generate a win. It works when matching symbols appear anywhere on the board in a valid payline pattern. Once it lands in a combination, it expands vertically, potentially completing lines that single-cell symbols couldn’t reach. Every expanding symbol win is multiplied by the value assigned during the cube roll, which means the initial selection shapes the entire round’s potential.
Land one wild during Free Spins for 5 extra spins, three wilds for 10, and four wilds for 15. The retrigger system keeps rounds alive longer than single-trigger games, and theoretically allows extended play. However, the 5,000x maximum win cap triggers an automatic end if reached, forfeiting any remaining spins. It is a hard stop designed to protect the operator’s margin.
Buy Free Spins directly for 100x your stake. The scatter odds favour a three-scatter trigger at 95.94%, with four scatters at 4.00% and five at 0.06%. The RTP during a buy sits at 96.01%, barely above the 96.00% standard rate. Our session returned 7.4x on a 100x purchase, which underscores the variance involved.
Everything about this slot’s payout structure is filtered through one number. The 5,000x maximum win cap means even a perfect Free Spins round with a 100x multiplier has a hard limit, and the game will end mid-feature if you reach it. That changes how you read the volatility rating. Five out of five bars sounds dramatic, but the cap constrains the upper end of what high volatility can actually deliver here. Bets range from €0.10 to €100.00, and the game pays left to right on adjacent reels from the leftmost position. Multiple payline wins on a single spin combine into one total, with only the highest win paid per line.
Every figure here assumes a €1.00 wager. Scale proportionally for your chosen stake level.
| Sun | €250 |
| Wild (Book/Astronaut) | €250 |
| Earth | €100 |
| Jupiter | €40 |
| Moon | €25 |
| Ace | €15 |
| King | €15 |
| Saturn | €10 |
| Queen | €6 |
| Jack | €5 |
| Ten | €5 |
This game is listed at 96.00% RTP during standard play, rising marginally to 96.01% when using the Buy Free Spins option.
Book of the Universe borrows a proven format and wraps it in a cosmic theme that looks adequate but never feels essential. The cosmic cube is a clever twist on the pre-Free Spins selection, but everything surrounding it is too generic and too stingy to leave a lasting impression. A disappointing session with a 7.4x return on a 100x bonus buy only confirms what the numbers suggest.
The bonus buy moment tells the story. We dropped 100x on immediate Free Spins access and watched the cosmic cube roll a 2x multiplier with a mid-tier expanding symbol. Ten spins later, the total win screen read 7.40 on a €1.00 bet. That is a 7.4x return on a 100x investment, and the deflation of watching that result screen appear after the cosmic fanfare of the cube animation was the most memorable part of the entire session.
Outside the bonus, regular play felt sparse. Card royals landed with predictable frequency while the planet symbols appeared just rarely enough to remind you they existed without actually building momentum. The space visuals are competent. Planets glow, the sun glistens, and the futuristic styling is themed well enough to hold together. But it is not the kind of visual treatment that makes you forget you are watching reels spin. After 40 or 50 spins without a feature trigger, the cosmic backdrop starts to feel like wallpaper rather than atmosphere.
The cosmic cube itself is the one genuinely interesting idea here. Rolling both the expanding symbol and the multiplier in a single animated moment creates a brief spike of anticipation that most “Book of” slots spread across the entire round. The problem is that the spike fades quickly when the multiplier lands at 2x and the expanding symbol is a low-value royal. The system works, but the outcomes rarely match the drama of the presentation.
Where Book of the Universe struggles most is identity. The space theme is decorative rather than structural. Nothing about the gameplay changes because planets are on the reels instead of pharaohs or explorers. The cosmic cube could exist in any setting. The expanding symbol format is borrowed wholesale from a dozen other titles. Strip the skin away and there is nothing underneath that you haven’t played before, and probably played better in games with higher maximum win potential or more generous feature frequency.
If you are specifically drawn to high-volatility “Book of” slots and want one with a space aesthetic, this fills that gap. For everyone else, the 5,000x cap, infrequent hits, and underwhelming bonus buy returns make it difficult to recommend spending extended time here when the genre has stronger options available.