When a Bible burns you to the touch.
Which can make for a great practical joke.
Especially if you can figure out how to heat up a book without burning it.*
If you can do that, you've also got a great new marketing opportunity.
"Smokin' hot Bibles for sale! Trick your friends into thinking they're evil, when in fact it is you who are the evil one! Fun for the whole family!"
* One way to accomplish this: make a deal with the devil.
(Much more practical than the alternative: make the book out of metal.)