One of my holiday books was John Scalzi's Old Man's War.
I actually got the book as part of the Humble eBook Bundle, a charity event I participated in last October.
Old Man's War sat around on my Kindle, gathering bits, for a few months, until I found some reading time over the holiday break.
I think that the publisher's blurb does a great job of describing Old Man's War:
John Perry did two things on his 75th birthday. First he visited his wife's grave. Then he joined the army.
The good news is that humanity finally made it into interstellar space. The bad news is that planets fit to live on are scarce--and alien races willing to fight us for them are common. So: we fight. To defend Earth, and to stake our own claim to planetary real estate. Far from Earth, the war has been going on for decades: brutal, bloody, unyielding.
Earth itself is a backwater. The bulk of humanity's resources are in the hands of the Colonial Defense Force. Everybody knows that when you reach retirement age, you can join the CDF. They don't want young people; they want people who carry the knowledge and skills of decades of living. You'll be taken off Earth and never allowed to return. You'll serve two years at the front. And if you survive, you'll be given a generous homestead stake of your own, on one of our hard-won colony planets.
John Perry is taking that deal. He has only the vaguest idea what to expect. Because the actual fight, light-years from home, is far, far harder than he can imagine--and what he will become is far stranger.
Old Man's War was such a success that Scalzi wrote a number of sequels, and the book is still hugely popular nearly 10 years after its original publication.
I don't read a lot of science fiction, but if more of it were written like Scalzi's work, I probably would. Old Man's War is a great read, with lots of action and adventure.
As with most science fiction, Old Man's War starts with a premise, a "what if?" question, and explores the implications of a world in which that question is answered.
And, as with most (good) science fiction, it turns out that Old Man's War is mostly about other topics, anyway, and the entire story and its themes are metaphor for much more traditional events back here on Earth. In this case: war, age, love; the same things that fascinated Shakespeare and Tolstoy back in their day. What's old is new again; in Old Man's War, literally!
If you like science fiction, I'm sure you're already quite familiar with Scalzi's work. But if you're like me, and don't pay that much attention to science fiction, but enjoy a good book, give Old Man's War a try; you'll probably enjoy it.