Last year in this post I commented on some of the so-called classic SF books I've managed to read over the past couple of years. I've got through several more in the past few months:
Helliconia Spring - Brin Aldiss - Excellent, but not quite as ground-breaking as perhaps it was at the time
A Fire Upon the Deep - Vernor Vinge - Brilliant. It was like reading 2 fantastic novels simultaneously.
Slaughterhouse 5 - Kurt Vonnegut - Original and quirky, but I was left underwhelmed
The Windup Girl - Paulo Bacigalupi - Brilliant.