I think Uruk is right, really. It's hard to read even the first few chapters of Cunningham's Evermeet: Island of Elves and not wonder if she checked any sources at all for what D&D deities are capable of. It's that sort of thing in her stories.
Personally, this is one of my major pet peeves with quite a few D&D novels, and their authors. Lynn Abbey and the Chronicles of Athas series, J. Robert King and the Blood Wars trilogy, Gene de Weese and Lord of the Necropolis, it goes on and on. All of these authors either didn't read or disregarded something fundamental about the subject matter of their writing, which, for me, lessens the novels enjoyment value considerably. When I read a book about the Planescape setting, I want to know that it's going to conform to the basic rules of that setting...otherwise why even call it a Planescape novel to begin with?
Admittedly, this is further than what Uruk was talking about. I'm going on about novels that break the rules of their settings, whereas he (I think) meant things that just didn't "feel" D&D.
I'm going to get crucified for saying this, but I've always felt that way about Weis & Hickman's work. They never seemed to particularly care for D&D, focusing more on the tone of the stories they wanted to write, and less for the absolutes of the world/universe that it was set in. Examples of this show up again and again in their works, and attitudes to related works of others. Their flat-out denial of Soth in Ravenloft, their use of Fizban in some of the Deathgate Cycle books (and a brief nod to that at the end of the Legends trilogy), their rather contemptuous lack of note for Jean Rabe's excellent Dragons of a New Age trilogy...no, I don't like Weis & Hickman much at all, for the same reasons as Cunningham.