Hmmm, what to recommend...
It's been a long time, but if you've never read Stephen Baxter, you're missing on one of the hardest of hard SF writers. He's mostly known for his
Xeelee series, which comprises a boatload of various novels and even more short stories collections, but he's written stuff like
Time's Tapestry (how our entire history is the result of a ... let's not spoil it too much then), and other.
Basically, anything by Baxter is worth reading, including his collaborations like
The Long Earth...