I haven't read the book, and have no plans to either. The story behind Eragon is a pretty standard one among the fantasy genre, and as a result isn't terribly original. The dragon characteristics are pretty much taken from Anne McAffrey's Dragonriders of Pern series (although I did think feathers on a dragon was a little odd), and there are other familiar elements to the story. Plot and character wise, it's pretty cookbook. CGI work on the dragon was well done. Monsters and goons could have been done better. You get the impression that most of the FX budget went to the CGI effects, leaving not much for goon costumes and makeup. Jeremy Irons puts in a good performance, and John Malkovich is pretty good as the villain.
Kids will probably enjoy this movie more than adults, particularly if they're fans of the book and can overlook the parts of the book that were probably left out of the movie.
3 stars out of 5.