The Amazon.com product description:
Retired from his fighting days, John Perry is now village ombudsman for a human colony on distant Huckleberry. With his wife, former Special Forces warrior Jane Sagan, he farms several acres, adjudicates local disputes, and enjoys watching his adopted daughter grow up.The Last Colony is the sequel to Old Man's War and The Ghost Brigades, both fine novels of science fiction that could well go on to be classics. This third book in the series was just as good, keeping me up until I got it finished (around two in the morning). There's a timeless feel to these books that makes me think that they could last. I've seen comparisons to Robert Heinlein's books in other reviews, and there is definitely something of that style here.
That is, until his and Jane's past reaches out to bring them back into the game — as leaders of a new human colony, to be peopled by settlers from all the major human worlds, for a deep political purpose that will put Perry and Sagan back in the thick of interstellar politics, betrayal, and war.
In terms of the story, this book picks up a few years after the ending of The Ghost Brigades, with John Perry and Jane Sagan living together in a colony with their adopted daughter Zoe. Although they're retired, it turns out that their adventures are nowhere near over. Not by a long shot.
I think for this book you really have to have read at least The Ghost Brigades, as quite a bit of the plot comes out of revelations and unanswered questions from that book. The Last Colony leaves quite the ending as well. One that feels like it could be the end of the series (and a satisfactory ending, too) even though there is a fourth book out: Zoe's Tale.
Overall, I've really enjoyed reading John Scalzi's books and if you like science fiction, I'd hope you'll give them a try. I'm certainly going to hunt down his other books in the future.