Book stealers are usually book resellers, usually on a street corner (if in a large metro area), a flea market or to an unscrupulous bookstore that buys stolen merchandise. Over the past 40 years, I've worked in bookstores only to learn that no book is impossible to heist. A pile of Herman Wouk's "War and Remembrance" took a hike one afternoon with a fellow who simply put his raincoat around a stack and walked out of one Manhattan store. We found him hawking them two blocks away for $2 a pop. I have also handed a customer an expensive book, turned my back for a moment and ... poof!...he was gone; I caught up with him a couple minutes ... and blocks ... later.
An article in the London Times earlier this year had a bookseller claiming that London A-Z was the most stolen book in the world. Maybe for him, or for his time selling books, but I'd like to see proof. Maybe it only holds true if you sell books in London, but I'd think it would be the Harry Potter books in England.
I put the whole book-stealing thing on '60s radical Abbie Hoffman who titled his tome Steal This Book, thereby encouraging rampant bibliocrime.
Of course, if one were to steal a book you'd think it would be something rare and valuable -- some first edition of some antique manuscript that was worth a fortune. But in my experience, the most-often pilfered book is the Holy Bible (King James version). Whether it has been from a small independent or a large chain store, it always seems that the most taken is the (supposedly) most sacred.
One wonders whether the people who steal bibles actually get around to reading them,. They might want to check out Exodus 20: 2-17. There are a bunch of Thou Shall Nots they should probably become acquainted with.