There are a lot of layers here, and I think that what Eugenides is trying to do is very smart, but the story just didn't hold my attention. Since I never was a big fan of the "marriage plot" novels to begin with, maybe I should have known this book wouldn't be for me. I initially liked Madeleine, though I didn't particularly care for either of the men and couldn't really see why any of them were attracted to one another. I also initially enjoyed the literary theory references in the first chunk, but after a while Eugenides took it too far and I began to find it annoying. The plot ultimately felt stagnant, even after Leonard's manic depression was revealed, and I couldn't sympathize with the characters at all.
Maybe I'm just not the right audience, but I did not enjoy this one at all.
ETA: Ugh, this review says it so much better than I could ever attempt to: http://nplusonemag.com/stuck-in-the-stacks