(My wife was a little worried when she saw this title. I assured her that it is not about THAT kind of divorce!)
More a short story than a book. Read this first several years ago, but re-read it recently. The narrator finds himself in Hell, although no one there really realizes where they are. He takes a tour bus to Heaven with some others from Hell and records his observations. The citizens of Heaven try (and fail, for the most part) to convince the souls from purgatory to cast off their sins and small-mindedness and journey with them to the far-off mountains of glory.
Heaven does not exclude anyone; rather each individual excludes himself by refusing to give up sins like intellectualism, pride, lack of faith, and selfishness.
Lots of symbolism in the story, but also a lot of plain old truth. An interesting read that makes you think!