The Book of the Dead is similar to the Udjat Eye, in that it helps you locate a secret level exit to take you to bonus stages.
In ]]Olmec's Lair\\ on level 4-4, there will be a secret door somewhere just above the lava at the bottom of the map which leads to Hell.
It will only open when the Spelunker has the Book of the Dead in their inventory.
The Book of the Dead can be used to find the location of the door before it comes into view.
When the Spelunker nears the spot directly above the door, the cover of the Book will start to become agitated. The spot at which the face on the book writhes the fastest is that directly in line with the door.
To access the door, the Spelunker must defeat Olmec by causing it to fall into the lava right below the door. He will have to break through ten layers of bricks to create a hole deep enough for the Boss to fall through, and then stand on top of Olmec as it sinks into the lava.
This is the only way to enter the door, as there is no ledge below it and hence cannot be reached without something to stand on.
- The Book's appearance is modeled after the Necronomicon as depicted in the Evil Dead franchise.