Yes, Shrek was a book first. I haven't read it, but it's fairly obvious that the film is very interested not just in the lore of one character, but that of fairy tales in general. They make adaptations on a very large scale, with characters including the Gingerbread Man, Captain Hook, and the Three Pigs. While the jokes run aplenty, what the filmmakers were able to do was incorporate these childhood staples of stories into a new film without abandoning their source material. They remain respectful, but add dimensions. They're not even worried about telling those stories, they just assume that we are already aware of them and use that knowledge to build, rather than perpetually recite. This is very much something Star Wars can benefit from. A new Star Wars film should't take the time to explain all of Han Solo's badassness. It's better to leave it implied and, if the movie chooses to give the character the time, build new dimensions instead of relishing in the days of old. Or, more aptly titled, days of which we've already seen. The Narnia films, as well, are book-inspired. It's another adaptation from preexisting source material. And it's done respectfully and on a grand scale. When it comes to source material, there are few properties that as well-guarded as that of the Star Wars franchise. So, a director who understands the source material and has experience in adaptation is a must. It's not necessarily a cry to be 100% faithful, it's a request that the material will remain respected, while being invigorated for a new (and old) audience. Let's not forget that with a projected release date of 2015, the newest Star Wars will come a full decade later than Revenge of the Sith. That's a whole decade of fresh eyes, and you've got to relate to them, as well.