Look at my life, I'm a lot like you were

Alright, so first with the friendly. Old Man's War is an updated Heinlein novel. Specifically it reads like Starship Troopers being written by a very optimistic Richard Morgan. It is set a few centuries in the future, where Earth is a backwater. Senior citizens are recruited to join the powerful Colonial Forces, with the chance at being young again. Our recent Medicare recipients are quickly thrown into some really rather nasty battles. The Morgan like feel comes from the brutal battle descriptions and unpleasant view of galactic society. It is happy Morgan though, because the author doesn't dig too deep into the unpleasant reality or allow the characters to dwell on it too long. He also has a few interesting technological ideas. The reviews of this book have been largely positive. The one negative one I read focused on the fact that society 200 years from now is very similar to our own. Large states and their corporate partners engage in large scale war involving soldiers and space ships. If you want a future society that has developed in a revolutionary rather than evolutionary path then look towards books by Ken MacLeod among others. If you want an intelligent space shoot em up, you will find few better than this one.