Book curse

Your story will be working toward your character finding the following written on the inside cover of a book:

"For him that stealeth a book from this library, let it change into a serpent in his hand and rend him. Let him be struck with palsy and all his members blasted. Let him languish in pain crying aloud for mercy and let there be no surcease to his agony till he sink to dissolution. Let bookworms gnaw his entrails in token of the worm that dieth not, and when at last he goeth to his final punishment, let the flames of hell consume him for ever and aye."

Where your story begins is with a corpse that has died in agony. Your character is the town's investigator. (The setting can be any time or place, real or imagined.) But what has caused the death? Is it some weird disease? The first incidence of a plague? Some tortured contract killing? Are curses known in your world but this is something far more powerful?

Are there more killings? Why have they begun now?

When you find the curse, why was it written? Was it a joke? Was one book magical that turned a joke real?

If your writing takes you in a different direction than the book, that's great too :-) You might find an even better answer to the unusual death. Sometimes writing does that :-)

(In the Middle Ages, books were protected by curses. The above came from the Monastery of San Pedro in Barcelona. You see that one and several others at Book Curses. Pages on the internet are ephemeral, unlike the above curse, so if that link sinks to dissolution, just search on the beginning of the curse and you'll find plenty of protection for your books.)