"This Momentary Marriage" (John Piper) - I like reading John Piper. His love for God is evident, his passion flows off the page. And his beliefs are similar to mine, but not identical - so I am always looking for how he comes to the positions he does.
This book is an overview of how marriage glorifies God. It covers many topics, and is intended to help a couple think about what they are committing to.
And it's number one focus is on the glory of God :)