The premise of the book is a series of letters and eventually a meeting between the archangel Michael and Lucifer.  They write each other and finally decide to meet on some unknown planet.  Michael tries to convince Lucifer to stop his rebellion and come back to heaven.  Lucifer counters that he can’t believe God created and loves and died for filthy mankind and that he wants to just destroy them all and wants nothing to do with God.  Fascinating book and really makes you think.  Caldwell is a great writer and this book is both provocative and fun to read.  Not sure it’s in print anymore, but if your local library has it, it’s definitely worth getting.