Believers should love to read and delight in God’s word. The Bible proclaims amazing doctrines (like the doctrine of God, or the doctrine of salvation). Sometimes it is especially helpful to acquire a good book on a theological topic that will do good things for your soul. Books by authors who love the Bible can greatly aid the believer on the spiritual journey. Check out this statement from C. S. Lewis:
“For my own part I tend to find the doctrinal books often more helpful in devotion than the devotional books, and I rather suspect that the same experience may await many others. I believe that many who find that “nothing happens” when they sit down, or kneel down, to a book of devotion, would find that the heart sings unbidden while they are working their way through a tough bit of theology with a pipe in their teeth and a pencil in their hand” (from his introduction to On the Incarnation by Athanasius).
In your devotions with the Lord, never abandon delighting in God’s word first and foremost. But find a book of great and profound theology, and read some of it every day also. Chewing on doctrine is good for your soul, good for your walk with the Lord. Chewing on doctrine keeps your mind sharp, and it helps you process what you believe from the Bible.
If you are interested in a good book to start for incorporating doctrinal books in devotional times, try including one or more of these: Knowing God by J. I. Packer, Mere Christianity by C. S. Lewis, Desiring God by John Piper, Christian Beliefs by Wayne Grudem, The Pursuit of God by A. W. Tozer, The Knowledge of the Holy by A. W. Tozer, or How to Read the Bible for All Its Worth by Gorden Fee and Douglas Stuart. There are countless more I could recommend.
Devour doctrine for your soul. It will shape your mind and heart, which will impact your life. Happy reading.