Unfortunately, I never bothered to look up a reading order for Asimov before I started the foundation series. So I've read the foundation trilogy, foundations edge, and I just finished foundation and earth. For some reason I don't feel very compelled to read the prequels, and I can't explain why. I'm more interested in the continuation of the series written by a different author (foundations triumph, etc). Now I've come to realize the robot books he's written tie into the foundation books. I'm just trying to decide whether it's worth going back and reading the main robot trilogy as well, at least before I read the continuation trilogy. Thanks!