Formal Titles:
* Librarian: This is the most common and accurate term for someone managing a library collection, which can include books and other materials.
* Curator: This term is usually used for managing collections in museums or art galleries, but it can also apply to someone managing a specialized book collection like a rare books archive.
* Archivist: If the collection focuses on historical documents, including books, an archivist would be the most appropriate title.
Informal Titles:
* Book Manager: A general term that could be used in various contexts.
* Collection Manager: Similar to Book Manager, but broader, encompassing different types of collections.
* Head of Collections: A more formal title that emphasizes the person's position of leadership over the collection.
The best title will depend on the size and nature of the book collection, the institution or organization it belongs to, and the specific responsibilities of the person in charge.