Old Man's War came recommended to me, and I was already knowledgeable of the author via Twitter, his blog and all that. I didn't have any hype build-up behind the book other than "Hey, all my friends have this 4 or 5 stars." That said, I enjoyed this enough to start paging through it again even though I just finished it - a good sign for me. I won't bore you with plot details, you can click the title of the book up there to read that if you want. I liked the 'Old Farts', the twists were twisty, and the emotional stuff with John's wife and not-wife worked.
It's an interesting companion to Ender's Game what with the widely divergent ages of the heroes. The subsequent Ender books deal with the difficulty of communicating aliens, and whether it's even possible for humans to have a lasting peace with them. The powers that be in the Colonial Defense Forces have decided the heck with all that, and pretty much just kill all aliens on sight. This was touched on a points, but I hope the future books which I haven't read yet go into more detail.
All in all, a fun 'quick' read for me, in an interesting world. I want to see more of it.