Although Morse corrects Lewis's English pedantically at one point, he is himself guilty of a solecism later on, when he asks Lewis to "appraise" him of any facts he may uncover. He meant to say "apprise", a quite unrelated verb.
When Morse asks to borrow a book from her bookshop, Claire Osborne comments that "this isn't the Bodleian". But, the Bodleian Library is in fact not a lending library, and all books there must be read only on the premises.