He who lends a book is an idiot. He who returns the book is more of an idiot.

This wry proverb plays on the everyday frustration of lending books: once a cherished volume leaves your hands, it may never return, or it may come back damaged. Calling the lender an “idiot” humorously acknowledges the naïveté of trusting others with something personally valued. The second line sharpens the joke by suggesting that returning a borrowed book is even rarer—or even socially awkward—implying that borrowers often keep books through forgetfulness, attachment, or mild opportunism. Beneath the insult is a comic commentary on human nature, property, and the sentimental bond readers form with their books.