As I've now finished volume four of Phillip José Farmer's The Dungeon, subtitled The Lake of Fire and written by Robin W. Bailey, I think I'm finally getting the hang of the series. Each new writer looks at the stuff that came before, and then moves the main characters to an entirely new setting, hopefully putting them back the way they were when the writer began his particular entry in the series (not an uncommon issue for comic book writing, come to think of it).
Some of the writers have been pretty great at this, my favourite being Charles de Lint, who split the group in book three allowing the story to bounce back and forth between the groups, only to reunite them in the last chapter before sending them on to the next world.
Volume four takes place mostly in a hell-like world (including devil and demons) and actually tests the characters beyond mere survival, which in itself was pretty neat, as well as reminding the reader that although Major Folliott is our main character, every other member of the group has their own goals and intentions, which should all be taken into account as well.
The fourth book was a pretty strong entry in the series, and has me looking forward to checking out book five.