Foundation is good. I found it a little harder to stay with it than I Robot, but then again, it's a much broader work. Each part of Foundation is pretty well self-contained though, as a story. And the trilogy taken as a whole is pretty damn epic. I don't really dig on a lot of sci-fi, but I liked it.
I won a prize for my review of Foundation And Earth, in the educational establishment I was at when I read it... (Came out 1986? Must have been in the library pretty sharpish to fit within the time-scale I remember...) I hadn't, at that time, read any of the other Foundation series (though I had trawled through many of the imminent-future Robot-era books, and Caves Of Steel (at least) from among the longer-future Spacer-era books, so I wasn't totally in the dark. I must have read at least some of the pre-Foundation Empire-series set as well, but my memory is hazy. Also can't remember whether I knew of R. Giskard's mind-breaking actions prior to reading F&E (has some small part to play in the description of the mythical Earth), but I definitely know about his 'disciple', (from CoS alone or a couple of the sequels as well), so I knew who he was when I met him.
Anyway, I later read all the rest of the Foundation set, without feeling 'spoilt' as to the conclusion, and have quite recently re-read everything I could get a hold of in 'order' (story-chronological, that is, near as I could arrange), but still found them totally unspoilt by foreknowledge. The story's the thing. And, after all, psychohistory is inexorable[1] (excepting the influence of extraordinary individuals[2]) in this universe, so there should be no problem accepting the future as written...
[1] With guiding hands. But guiding hands which are themselves guided, so it probably still stands!
[2] Of at least three different kinds, that is. Only one of whom might be considered human, and one might not even be considered an individual. BYSWIM.