Actually, it wouldn’t strictly be a return… he bought it from a non-chain store in a city kinda far away and we can’t return it to the source. It’s a popular book in some circles (the third of the Twilight series of books—Eclipse), so there theoretically should be some demand for it, but the recipient is not a fan and would much rather she get something she’d actually enjoy.
Borders have been lenient and allowed me to exchange for store credit. I buy a few hundred dollars worth of books from them each month, so it is worth allowing me this one small exchange each year - and they can resell the book.
As long as the book is in saleable condition, any bookstore will take it back, either for store credit or a refund (not so much if someone inscribed it).
Their books are there on consignment, anyway: you’re just doing what they’re doing. They can return the book to the publisher for store credit, especially if they have copies of the book in stock. (It probably won’t matter if they don’t, since the publisher/wholesaler isn’t going to check their records very hard.)
Borders won’t take it back. At least, they didn’t take my book back when I tried something similar (Outliers, with a Borders sticker on the front: “30% off all hardcovers!” or some such). They required a receipt.
I won’t give an exchange or refund without a receipt. People will swear blind they bought something in my store, sometimes when it is still in the wrapper from our competitors!