Well, no wonder!
Link to December 3 San Jose Mercury News article, "Library book returned with a little something extra: $7,600".
Excerpt: Donna Nguyen, a clerk at the Santa Teresa Branch library in San Jose, noticed something strange when she was sorting returned books the Saturday after Thanksgiving.
A copy of "The Little Mermaid" was heavier than it should have been. And when Nguyen flipped through the book, she was stunned to find it stuffed with $7,600 worth of $100 bills.
She told her bosses, and they stored the money in a safe place until the relieved customer could retrieve the cash.
Apparently the money was stashed inside the book by a grandmother for safekeeping -- and not just payment for a really, really overdue book.