Phthor is the second in the Aton series and sequel to Piers
Anthony's first published novel, Chthon, less intricately
structured and less complicated in plot, but still quite dark and
ugly in theme and detail. Rather than flashbacks and
flashforwards, it has a Y outline, with the stem the initial story and
the ends alternate futures, neither of which is acceptable to
Aton’s son Arlo.

From what I read of the blurbs at the site, I'm glad I never wasted time on the originals.