Picked up a beaut from 1977, "Gateway"
by Frederick Pohl. Won the 1978 Hugo award for Best Novel.
One of those wonderful 70s covers too (this is the edition I have - I was going to take a photo of it but Wikipedia had this nice one already)
It's a first contact story, sort of, and I quite enjoyed it. It was quite progressive for the time regarding human sexuality (not in a sort of creepy Heinlein way, but in a legitimate "making a liberal statement" way). I think the only flaw that bugged me the whole way through was the underestimation of human ingenuity - I figure that on the time scale in the book, with the resources being pumped into (and out of...) Gateway, people would have made a lot more progress figuring out how it all worked.
The format of the story was interesting. The protagonist starts out visiting a robot psychologist (and narrating the story in the present tense, which was jarring at first but quickly became normal) for odd-numbered chapters, and progressing through his past on even-numbered chapters. You're unsure at first exactly what's wrong with him, and why he's not satisfied with his outwardly fantastic life, but as the story of his past progresses, it all unfolds. The ending was very satisfying.
Apparently it's also being developed by Syfy
, as of last year.