Yes, it is accurate to describe the Bible as a supernatural book. For example, Jesus said, quoting Deuteronomy 8:3, “Man should not live by bread alone, but by every word that comes out of the mouth of God” (Matt. 4:4). So, the ultimate source of the Bible is God Himself. The Bible is supernatural.
But at the same time, the way in which God’s Word comes to us is through the lips or the pens of men. I think that is well summarized in what God says to Jeremiah: “I am going to put My words in your mouth. They will come out of your mouth. You will speak them, but they are My words.”
In the Scriptures, there is a beautiful combination of the authoritative voice of God coming to us not only through different personalities, but even through different literary genres like history, poetry, narrative, epistles, and apocalyptic books like Revelation. I think God does that so the way in which His Word comes to us through human beings will draw out the whole of our humanity to love Him, to love His Word, and to serve Him.