One of the most fun series I've read is the Galactic Football League series by Scott Sigler. Sounds corny, I know, but
it's terrific. Very fun with a hard science fiction background. Think of Star Wars meets the NFL meets The Godfather. Very fun, and it gets me through the off season. The series is six books long, with five already published, and begins with The Rookie.
The universe Sigler has created is amazing. I can't recommend it enough. I'm reading them all for the second time around.