Your 5 should be somewhat diverse. In other words, don't give me 5 books on theology only. Mix it up. And I know you want to list more than 5, but no cheating! Don't necessarily suggest your best 5. Get creative. Mention some others won't mention.
Here are my 5, foundational-ish ones...
The Reason for God by Tim Keller
Knowing God by J.I. Packer
Desiring God by John Piper
Putting Amazing Back Into Grace by Michael Horton
Spiritual Disciplines for the Christian Life by Donald Whitney
Your turn. No need to add links unless you want to.