IPA: /ˌbɪbliˈmeɪniæk/
KK: /ˌbɪbliˈmoʊniˌæk/
A person who has an extreme enthusiasm or obsession for collecting books, especially rare or valuable ones.
The bibliomaniac spent all his savings on rare first editions.
Bibliomaniac → It is formed from "biblion" (from Greek, meaning book) and "mania" (from Greek, meaning madness or obsession). The word describes a person who has an obsession or madness for books.
Think of someone who has a 'madness' ('mania') for 'books' ('biblion') — that's why bibliomaniac refers to a book lover with an obsession.