I have thought about this question for at least twenty years, Elisa Gabbert spells it out (NYT):
My favorite spot in my local library — the central branch in Denver — is not the nook for new releases; not the holds room, where one or two titles are usually waiting for me; not the little used-book shop, full of cheap classics for sale; and not the fiction stacks on the second floor, though I visit all those areas frequently. It’s a shelf near the Borrower Services desk bearing a laminated sign that reads RECENTLY RETURNED.
This shelf houses a smallish selection of maybe 40 to 60 books — about the number you might see on a table in the front of a bookstore, where the titles have earned a position of prominence by way of being new or important or best sellers or staff favorites. The books on the recently returned shelf, though, haven’t been recommended by anyone at all. They simply limit my choices by presenting a near-random cross section of all circulating parts of the library: art books and manga and knitting manuals next to self-help and philosophy and thrillers, the very popular mixed up with the very obscure. Looking at them is the readerly equivalent of gazing into the fridge, hungry but not sure what you’re hungry for.
Is it better to spend time, at the margin, pawing through the “recently returned” cart, or the “New Arrivals” section or for that matter just the regular shelves? How about the books simply left on tables and abandoned?
The big advantage of the books on the carts is that they usually are not bestsellers. For bestsellers there is a waiting list, and they are held for another patron, never making their way to the cart. I say go for the carts.