I've also found he begins better than he ends. The first Incarnations of Immortality book (On a Pale Horse) was excellent, and some of the others were okay, but they took a definite downturn. The Xanth series also started strong and went steadily downhill. The Adept series was really great for the first set, but one of the books (I forget the title) of the second set actually made me do something I've never done: I actually put the book down in the middle and decided I couldn't stand to read anything else from this man. I haven't read it since.

It wasn't moral outrage or anything (though I think the scene in question was sexual; I have no problems with that). It was much more simple than that. I was just sick of his juvenile world-view and writing style. He has some lovely ideas that start off making wonderful worlds, but always pollutes the storylines with childishness. This is great at the beginning, as childishness can make for enjoyable reading, but it gets sickening after a while, and starts to take over.