It's been sooo long since I've seen an author take a real crack at telling a true hard s.f. space opera. These can be tricky to write, requiring a story with a great deal of momentum, some strong characters, thorough world building, and a technical background. Happily Karl Schroeder has pulled it off in Sun of Suns, the first book of his Virga series.
This book just does everything right. It's full of some absolutely brilliant ideas (the book takes place in a contained, artificially created galaxy without any land), every character evolves throughout the course of the story, and there are even a few battles with air pirates thrown in for good measure.
It's been a long time since a book has left me this eager for the sequel.