There's actually slightly different versions of the Bible among different Christian denominations. Almost all of them include 24 books from the Tanakh or Hebrew Bible, though they are sometimes split up differently and arrange in a different order to form 39 books. These make up the Old Testament. There's also the Apocrypha which includes books not accepted as being part of the Bible but still valued by different denominations as being important or useful. There are then 27 books of the New Testament which almost everyone agrees on. You can read more at the Christian Biblical Canon wiki.