Read Red Mars. Am reading Green Mars.
They're really great. I was genuinely surprised about Red Mars being so enjoyable. I am okay with hard sci fi, but I tend to like it better in short formats. But I really liked Red Mars! I think the managing factor is how important the hard science is to understanding the story, the less the better. Red Mars is like this: undoubtedly you will enjoy it more if you really enjoy the scientific principals, but it's also a really great book about people.
That said, I'm kind of burnt out on "serious" stuff, and there's a lot of very sad moments in these books. I think I'm going to wrap up Green Mars, give Blue Mars shelf space, sending Red and Green to MC (hey, Met, PM me your address!) and starting Way of Kings.