Hell

In which Kate and Daniel go to Hell, on a mission from God.

Along the way, they visit the underworlds of several different religious systems, come to terms with where they've come so far, and learn more about the true nature of the mission that YHWH charged them with in the first book.

You really don't want to read this until you've read Heaven, the first book in the series, but I'd say this one was a more enjoyable read. It seemed a lot more focused, and Lafferty finishes it off with the most interesting of cliffhangers; I'm very curious to see where she takes the story next.