Exhaustion of copyright is pretty much what is known in the US as the doctrine of first sale. Only the copyright holder may sell a given book to the first buyer, but that buyer is then free to sell that copy of the book to anyone.
The EU's highest court has ruled that this does not apply to used e-books. There is some concern that this may be applied as a precedent against the resale of other digital media like games and movies.
Sale of second-hand e-books infringes copyright, rules CJEU