It might be much calling what follows a book, but Death's Head: Maximum Offense, by David Gunn (can you get a name better than that for military sci-fi?) is a quick and hugely entertaining read. The pace is break neck and it doesn't let up for a second. I found my self leaning forward in my chair, airline style, braced for impact. I finished this in one sitting, not because it was a must read but because its simple good honest fun.
The main character of this military science fiction novel is a muscular skin envelope stitched together to cover a ton and a half of pressurized testosterone, who leads a rag tag unit of dysfunctional super soldiers. Macho hardly begins to describe the protagonist--insane probably does. But boy o boy insanity is fun when you combine it with future tech and a frequent desire to exterminate your enemies, and generally anyone that's an annoyance.
Hive minds, godlike emperors, ring worlds, and desperation make this an enjoyable if slightly shallow read. Highly recommended if you just want to go along for the ride.
Here is a fairly comprehensive listing of military science fiction out there for those of you that might enjoy other titles. Enjoy!