In his recent podcast, Greg Koukl, of Stand to Reason gave a list of 7 books that together a sound Christian structure to thought and practice.
I've set out lists of recommended books, but Greg's is better. Mine are too 'me' and possibly not always helpful to others.
Here's Greg's list .
1. The basics of Christian faith
C. S. Lewis - Mere Christianity*
Greg Koukl - The Story of Reality*
2. Single volume theological reference
Millard Erickson - Christian Theology*
3. Christian Apologetics
F. Turek and N. Giesler - I don't have enough faith to be an atheist
W. L. Craig - Reasonable Faith*
4. Spiritual reflection
C. Spurgeon - Morning and Evening
A. Bennet - The Valley of Vision
5. Practical engagement
G. Koukl - Tactics*
6. Spiritual life
John Owens - Spiritual-mindedness
C. Lungaard - The Enemy Within
7. Bible study
G. Fee, Stuart - How to Read the Bible for all it's Worth
*I have in my library and have read them, except Erickson.