I recently watched all three original Star Wars films for the first time since seeing them in theaters in 1997 (I bought the DVD set in the fall of 2004). But before watching episodes IV and V, I read the novelizations, as I also did immediately after episode VI. In any such converstion of media, the source material is almost always superior, and this was no exception: the books were vastly dependent on the on-screen action to detail what was happening. The most enjoyable novelization of the three was Return of the Jedi, which offered some useful insight into the characters' thoughts: Han Solo's evolution toward selflessness; Luke's struggle with the Dark Side; Vader's machinations against both his son and emperor. I had hoped for a bit more detail into Vader's final redemptive act, but none was forthcoming.
The only other movie novelization I've ever read was Attack of the Clones, which had numerous exclusive scenes (both deleted from the movie and created by the book's author). I guess I was hoping for a similar treatment from the original trilogy.
In related news, IGN.com recently posted its "Top 25 Movie Franchises of All Time". George Lucas had the winning entry, of course.