I disagree entirely. The novel adaptations of the Star Wars movies are very much worth reading. They are by far the best Star Wars novels out there (IMO). They really add to the films.
In Episode IV, you get to know Biggs on a much more personal level.
In the Jedi novelization, the unspoken war going on between Luke and the Emperor on the Death Star is spectacular. And the Jedi novelization really deals with just how close Luke came to the dark side.
And the Episode 3 novelization is a great book and makes Anakin's fall much more realistic.
For me, the movie novelizations fix pretty much every complaint I had with the movies. Well worth reading.
Totally agree, I've read all the novel adaptions of the movies, and i have to say especially in Revenge of the Sith it gives you so much more background information.
I believe at one point they even explain why Obi-Wan was chosen to go after Grievous. That sort of extra detail really gives you a better understanding of what is going on and why.