“What are you doing with all these books anyway?” Ron asked, limping back to his bed.
“Just trying to decide which ones to take with us,” said Hermione. “When we’re looking for the Horcruxes.”
“Oh, of course,” said Ron, clapping his hand to his forehead. “I forgot we’ll be hunting down Voldemort in a mobile library.”

Harry Potter and the Deathly Hallows – J.K. Rowling