I ended up hating "incubus Master". I had to read it for a challenge, so I chose to suffer through it's 28 pages, instead of DNF-ing it.
I don't know if I've missed something, like the first two books, but it was very hard to figure out all comings and goings. "Incubus" reads like half a chapter yanked out from the middle of a book. It also needs some serious editing, but even then (this part at least) is not salvageable in my opinion.
Oh, and half of it is sex. Actually, it's PWP. No plot. Not that I could find. Maybe that's way it was hard to follow.