Hardcovers are generally returned intact. Paperbacks and magazines often just require that the retailer tear off the cover and return that, while destroying (at least in theory) the rest of the book. That's why you sometimes see that warning in the front of paperback books and magazines about not buying it if its cover has been removed... unscrupulous retailers will sometimes strip the cover, return it for credit, then sell the stripped book on the black market.

Book value on the balance sheet is ~$474 million, but that doesn't seem particularly meaningful in a valuation context for the business (especially considering the ~$1,123 million they are carrying for treasury stock).

As for inventory, they have that carried on their books for ~$1,000 million, which also means very little without a broader context on the state of the business.