I just finished reading Divorce and Remarriage in the Church: Biblical Solutions for Pastoral Realities, by David Instone-Brewer (Downer's Grove, Illinois: IVP Books, 2003).
This is the best book I have read on this subject. Instone-Brewer balances respect for the authority of the Bible, good historical background and scholarship with pastoral compassion. His arguments are consistent, logical, and biblical. Basically, he says that while the Bible discourages divorce, it is practical in allowing divorce and remarriage under certain grounds.
You can read his book on his website, www.Divorce-Remarriage.com, or order a copy of the book. Its well worth the investment if you or someone you love are dealing with this issue.