Eon by Greg Bear, and then its sequel, Eternity, which is about as good as the first book.
Tau Zero by Poul Anderson... set in the future, but with a good physics grounding.
I'm not sure it counts as hard sci-fi, but given its roots in Chernobyl Roadside Picnic by the Strugatsky Bros might be a good choice (it's also pretty short).
Tau Zero by Poul Anderson... set in the future, but with a good physics grounding.
I'm not sure it counts as hard sci-fi, but given its roots in Chernobyl Roadside Picnic by the Strugatsky Bros might be a good choice (it's also pretty short).
