You can see posts from readers wondering why authors let Hollywood change their stories pretty much every week on various SFF message boards. Ursula K. Le Guin offers some insight on the process that saw her classic Earthsea series get adapted for television. You'll see that most writers have little or no creative control whatsoever. . .
Here's an excerpt:
On Tuesday night, the Sci Fi Channel aired its final installment of Legend of Earthsea, the miniseries based—loosely, as it turns out—on my Earthsea books. The books, A Wizard of Earthsea and The Tombs of Atuan, which were published more than 30 years ago, are about two young people finding out what their power, their freedom, and their responsibilities are. I don't know what the film is about. It's full of scenes from the story, arranged differently, in an entirely different plot, so that they make no sense. My protagonist is Ged, a boy with red-brown skin. In the film, he's a petulant white kid. Readers who've been wondering why I "let them change the story" may find some answers here.