books 2010: Quest for the Well of Souls, by Jack L. Chalker
Book 3 in the Well World series. I liked the ending: everybody who deserved to die got killed, the good guys made it back to civilization (albeit in sexy woman form), and Mavra and Obie were released from their various prisons and get to go explore the galaxy together. I'm interested to read book 4 and see what happens to them.