Tim Challies provides an excellent review of Tim Keller's newest book, The Meaning of Marriage. Below is his strong conclusion, but go and read the whole review and buy the book.
This is a powerful book; it is my new favorite book on marriage and the best of all the books I read in 2011. The Meaning of Marriage elevates marriage, making it something beautiful and holy and lovely. And with it comes friendship and companionship and sex and everything else God has packaged into the marriage relationship. This book celebrates it all and it does it within the greatest context of all—the gospel of Jesus Christ.
Having read the book through two times, I’ve found myself wondering how to best measure or evaluate it, but perhaps these criteria are useful: Would I want to read it with my wife or would I encourage her to read it on her own? Would I recommend it to the people in my church? In both cases the answer is an unreserved yes. In fact, I bought the audio book and listened to it with my wife and her assessment is the same as mine: Though there are many great books on marriage, this is the one we will recommend first.