The Bible is not a book, it is made up of multiple books.
Hence why people aren't always clear on what is scripture and what isn't.
The cannon of the old testament wasn't clear for a long time, and even during the times of jesus, there was debate among the jews about the last part of the TaNaKh, aka the Ketouvim, as for what is inspired or not. This is the big difference between muslims and christians.
Muslims believe the Quran to be the Word of God in a way that makes arabic a holy language, because allah literally gave to muhammad a word for word transcription of the quran., of his Word
Christians believe that the bible is both divine and human, as Jesus, who is the Word of God. There's incredible parallels here if one digs a bit.
That is, because the bible isn't the literal Word of God, it is the "inspired" Word of God, and God can speak through men by his inspiration elsewhere than the Bible. But the Bible is the center of tradition, the center of God's inspired revelation.