I've never been a fan of Kesey, and having lived in the NW my whole life I have to admit I'm sick of hearing about him, so that may skew my opinions slightly. I think he's a decent writer, not a great one. I think he's mainly hype. (Please feel free to resist the urge to hit quote and reply to that statement now, these are my opinions. You can't and won't change them.)
It's not a bad book by any means, and it doesn't surprise me that it might be someone's favorite book, but 3/4 of the people sitting around a table seems a bit excessive to me. If you're interested in it, I'd reccomend finding a $0.99 copy at a used book store and give it a shot. My experience is that if it's not a book you're being forced to read in school, it's one you either read entirely or give up on comepletely.