For all their flaw, I really enjoyed the Xanth books when I was young. And a weird standalone book, But What of Earth, by Anthony is something I really loved. I never read the Incarnations books when I was young, so this was among the 'first books in a series that I missed out on at the time' that I decided to test out and see whether the series would be worth my time now.
I can definitely see Anthony playing with some of the same notions and techniques he uses time and again in Xanth, and even some shades of But What of Earth. And maybe, like a lot his other books, this just didn't age well (I try to set aside the intense misogyny I expected going on), but this book barely held my attention. I didn't care about the protagonist, most of the supporting characters, or their dilemmas (moral or otherwise). The characters I did enjoy had such bit parts (a few of the 'clients', a few of the ghosts) that it wasn't worth it, and the world building was really all over the place.
If you like Anthony, or other similar fiction contemporaneous to this, you might like it. Or enjoy it for nostalgia sake, but I'd say for the casual reader to pass, and I likely won't be finishing the series.