Glory Season, David Brin. Ok, this is one of the best. A heartrending saga of epic scale.
Carve the Sky, Alexander Jablokov. Scifi feudalism.
All of an Instant, Richard Garfinkle.
Vita Nostra, Marina & Sergey Dyachenko. Though very different, it somehow reminds me of Roadside Picnic.
Spin, Robert Charles Wilson.
Schismatrix, Bruce Sterling.
Interstellar Pig, William Sleator.
The Carpet Makers, Andreas Eschbach
The Threshold series (Peter Clines) doesn't really belong in this list, but it is excellent and from what I gather, commonly overlooked by fans of Lovecraft.
I'd also throw in The Sparrow, Mary Doria Russel, if it wasn't so well known already.
In a different vein, if you seek good-old action-packed, kick-ass never-ending fun, pick anything by Larry Correia. Even if it appears fantasy, it might turn out to be scifi...