biblioklept
A person who steals books.
rare
Thus Libri, who was the greatest of Biblioklepts, rescued many of the books he stole from dirt and misuse, and had them bound royally in purple and scarlet.
Where it comes from
From biblio- (“book”) + Ancient Greek κλέπτης (kléptēs, “thief”).
Adapted from the Wiktionary entry biblioklept (CC BY-SA 4.0).