Paul David Tripp, in his book Dangerous Calling, mentioned at least five kinds of books that we read:
There are explanatory books written to help you understand something that has left many people confused.
There are encouraging books written to speak into the discouragement of life in a fallen world and give you motivating hope and a reason to continue.
There are instructive books that help you know how to do something that you need to do but simply don’t know how.
There are exegetical books that take apart a portion of God’s Word, helping you understand it and to live in light of its truths.
[Then there is the] diagnostic book. It is written to help you take an honest look at yourself in the heart-and-life exposing mirror of the Word of God- to see things that are wrong and need correcting and to help you place yourself once again under the healing and transforming power of the gospel of Jesus Christ.
Jojo Agot 