Or to put it another way, which "book" in "the Bible" says which books are in the Bible? [nudge, nudge]
Actually, if you try to use the Bible as the basis for the canons of the Bible, you end up with some books that we don't have (like "The Book of the Wars of the Lord"), and other books that are not in the canon, like Jude's reference to Enoch.
What's more, if you use references in, say, the New Testament, you will end up with all of those books of the Old Testament that Protestant traditions call "Apocrypha", because there are about 118 references to the texts in those particular Scriptures in the words of Jesus and the Apostles.
Truth is, Pope Damascus decided which books were in the Latin Bible, in the late 300s. His choice was confirmed at Trent. The Orthodox have a few more books.