Book of Oil
- 🎰Provider
- Endorphina
- 📅Release date
- 21.09.2021
- 🎨Theme
- Фрукты, Монеты
- 📊RTP
- 96.05%
- ⚡Volatility
- High
- 💰Max win
- 5555x
- 📐Grid
- 5×3 · 10 линий
- 🪙Min bet
- 0,10 €
- 💸Max bet
- 45,00 €
- 🎮Demo
- Yes — free
- ⚙️Mechanics
- Wild Scatter Free Spins Expanding Wild/Reels Gamble Bonus Pop
Book of Oil slot review
Oil rivers shimmer gold under the sun, and the derricks are already crowded with polished tycoons in dark sunglasses — Endorphina dressed the classic book-slot genre in black-and-gold luxury and gave it the unmistakable scent of big money.
Book of Oil runs on a 5×3 grid with 10 paylines, high volatility (High), and an RTP of 96.05%. Hit frequency sits at 3.4, while the win ceiling reaches an impressive ×5,555 the stake.
What actually holds this game together?
The Book symbol here does double duty as both Scatter and Wild, a familiar setup for the genre. Winning lines are read left to right starting from the leftmost reel, with matching symbols required on adjacent reels in sequence. Scatter is the exception — it pays from any position on the grid regardless of paylines.
Where does the big win hide?
Three Scatter symbols landing anywhere on screen trigger a round of 10 free spins featuring an expanding symbol.
💡 How the expanding symbol works
At the start of the feature, a special symbol is randomly selected to become the centrepiece of the free spins. One important detail: during the bonus, the Wild cannot substitute for this special symbol — it remains its own separate icon. The special symbol expands after regular-symbol payouts are settled and pays for combinations of a kind in both adjacent and non-adjacent positions, though only on enabled paylines. Free games can retrigger during the feature itself.
A classic Risk Game is also available after any win, letting the amount double up to 10 consecutive times, alongside a Bonus Pop feature that adds an extra element on top of the base spins.
High volatility — what does it actually feel like?
With a hit frequency of 3.4, this slot is upfront about long dry stretches between meaningful wins — one of the lowest hit frequencies among the Endorphina titles reviewed so far, typical for slots with a ceiling above ×5,000. Most of the return here comes from the bonus round with its expanding symbol, rather than a steady stream of small base-game hits.
⚠️ The Risk Game cuts both ways
Doubling in the Risk Game works in both directions — a wrong guess wipes the accumulated round amount. The further you push the double-up streak, the higher the cost of a mistake.
What players love
- A ×5,555 win ceiling — among the highest of the Endorphina titles covered
- The expanding symbol in Free Games can build a genuinely large win streak
- Free games can retrigger during the feature
- Classic Risk Game with up to 10 consecutive doublings
Worth keeping in mind
- ⚠️ Availability of the Bonus Pop feature may depend on jurisdiction and casino
- A hit frequency of 3.4 is on the low end — expect extended dry stretches
- The Wild cannot substitute for the special symbol during free spins
- The Risk Game can just as easily wipe a win as double it
Who's cut out for this oil-fuelled luxury?
| Player Profile | Verdict | Why |
|---|---|---|
| Chases a high win ceiling | 🟢 Yes | ×5,555 is noticeably above average for this Endorphina lineup |
| Enjoys the classic book-slot genre | 🟢 Likely | A Book symbol acting as both Scatter and Wild is a familiar, tested mechanic |
| Prefers frequent small wins | 🟠 Unlikely | A 3.4 hit frequency is on the low end, with many dry spins between hits |
| Plays at casinos with feature restrictions | 🟡 Caution | Bonus Pop isn't available in every jurisdiction — worth checking in advance |
⚡ Is Book of Oil worth playing?
Book of Oil is a genre classic in a lavish package: the familiar Book-as-Wild-and-Scatter mechanic is paired here with a genuinely high ×5,555 ceiling. That potential comes at the cost of scarce hits — a 3.4 hit frequency demands patience and readiness for long pauses between wins. Players who appreciate the classic genre and don't mind waiting for a big haul should give it a serious look. Those hunting a steady flow of small payouts should look toward a less volatile option instead.
Game screenshots
Book of Oil FAQ
1
How are Free Spins triggered in Book of Oil?
The feature is triggered by landing 3 Book Scatter symbols. It awards 10 Free Spins, and at the start of the bonus round one special expanding symbol is selected at random.
2
How is the special Free Spins symbol different from a regular Wild?
The special symbol is randomly selected before the Free Spins begin and can expand to cover an entire reel after regular wins are paid. The Wild cannot substitute for this symbol, making it unique during the bonus round.
3
What does the Book symbol do in Book of Oil?
The Book symbol combines the functions of both Wild and Scatter. It substitutes for regular symbols in winning combinations and triggers the Free Spins feature when 3 or more appear.
4
Can you gamble your winnings in Book of Oil?
Yes. The classic Risk Game allows you to double your winnings up to 10 consecutive times. An incorrect choice forfeits the entire accumulated prize.
5
Does Book of Oil include Bonus Pop?
Yes, but Bonus Pop is not available in every casino. Its availability depends on the operator's licence and jurisdiction.
