Tor's free book this month is "Vernor Vinge’s Hugo Award-winning seminal space opera, A Fire Upon The Deep," aka that one book with space puppies. http://ebookclub.tor.com/

It probably won't be the most progressive or genre-bending sci-fi you ever read, but I enjoyed the playful what-ifs explored in Vinge's straightforward narrative style. It's a book that respects ideas above shock or surprise.