Well, technically it has become a book. But it wasn't a book in the beginning.
What do I mean? The earliest name given to the Bible is “biblia”—a Greek word for multiple “books.” Christians and Jews called the Hebrew prophetic writings “biblia” (Daniel 9:2; 2 Clement 14:2) before either group decided on a complete set of sacred books to use. In the Fifth Century AD Christians applied the term to all the books in the Old and New Testaments. The name “biblia” accurately communicated the variety of books considered Holy Scripture.
However, the plural name “biblia” changed over time into a singular term, translated into English as “the Bible.” That change has caused serious interpretation problems. Treating all the different books in the Bible like they communicate meaning in the same way is a category mistake.