I just finished the ROTS novelization last night. It wasn't the best Star Wars novel I have read, but it was pretty good. I thought the novelization for Episode II was fantastic compared to the movie. This one, while it had great parts, was not as impressive.
In my opinion, the first part of the book was toooooo long-the "rescue" of Palpatine on Grievous's ship Invisble Hand was action packed, but drug on for almost half the novel. I'm glad the film version didn't end up that long. There was some dialogue, especially between Palpatine and Anakin, that would have been nice to have included-just to further the implied friendship, and mentor relationship they had.
Once this section of the novel passed, the rest read really quickly. There were additional scenes, and dialogue that would have been very informative-especially bewteen Anakin and Padme, and Obi-Wan and Padme.
The last few chapters of the novel, I prefer the movie version of events. Starting when Palpatine reveals himself to Anakin-I liked the movie version much more than the book version, though it would have been nice for Anakin's quick turn to the dark side to have been played out a little more like it was in the book. This wouldn't have left audiences questioning why he turned so (apparently) fast. It is slightly implied in the film, that Anakin has been struggling with his fear, and anger for some years, but the book has the great advantage of being able to really explore this, with Anakin's thoughts. I really liked that aspect.
A few things I thought should have been included in the film-Palpatine admitting outright that Darth Plageious was his Master, and the scene where Yoda "talks" to Qui-Gon-just before Obi-Wan arrives with the injured/distressed Padme.

All in all, I liked the variation on the story, but I wasn't a fan of this particular author. I didn't really like his writing style, and that might be why I prefer the movie over the book. Whereas with Attack of the Clones, the book was much better than the film.