"But the Counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you."
The Bible is unlike any other book in that just can't simply read it and understand it. Although the words are physical the truths it conveys are spiritual so that to those who read it without faith may be "seeing but never perceiving" and "hearing but never understanding." This is God's judgment upon them lest they turn and be forgiven. (Mark 4:12; Isa 6:9.10)
However, they need but just confess their sins and they will receive the Holy Spirit who teaches them all things. God's judgment is absolute, but he himself in his mercy has allowed it to be circumvented through faith in His Son Jesus Christ. Now God himself has come down to teach us and empower us in the person of the Holy Spirit to obey that law which brings life. (Micah 4:2; Is 2:3)
The Holy Spirit guides us into all Truth (which is Christ) and reminds us of God's Word when we need it most. Man lives by every Word that comes out of God's mouth (Deut 8:3), and the Holy Spirit is the author of those words. He has spoken through his people and the result is the Holy Bible. The Word is Christ (Jn 1:1) and without him we shall surely perish.