The absolute best book to read in regards to marriage: Sacred Marriage: What if God Designed Marriage to Make Us Holy More Than to Make Us Happy by Gary Thomas
Gary Thomas is a Christian author, though not Catholic. He amazes me because he quotes the saints (esp. St. Francis de Sales and St. Thomas Aquinas) more than any CATHOLIC author I have read (on marriage). I was fortunate to hear him speak and spoke with him afterwards about his background.
I have read LOTS of books on marriage (Catholic, Christian, secular) and this one is by far the best. In fact I am selling ALL of my books on half.com but am keeping this book, a copy of Imitation of Christ, My Utmost for His Highest, and my bible. Everything else that doesn't sell is going to the second hand store or St. Vincent de Paul (over 500 books!!)
Gary Chapman's book on "love languages" is good but WAY too basic; definitely a "beginner" book. In order for marriage to succeed you will need more than just a "beginners course"..