During the Renaissance, due to "light-fingered Italian Humanists," ancient tomes would often go missing. Books were then on occasion 'guarded' with a curse in the preface.
I'm launching a book shortly, and I thought this would be an absolutely fabulous insert for the beginning.
For him that stealeth, or borroweth and returneth not, this book from its owner ... 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 sing in 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 forever.
It also probably wouldn't be a bad idea to tack the same sorta greeting over my own bookshelf.