When Joe is holding the Tolkien book it's a paperback, which his line also points out, but when the customer walks away with the book it's a hard cover.
15 minutes in, at the Dickens gathering, the guy in the blue/white checkered shirt and jacket following the Becks suddenly has no jacket and then instantly does again.
Joe mispronounces Tolkien's name (not likely for an educated bookstore owner to do).