Reviewing books in the middle of a series is always tricky because, by definition, spoilers are inherent. The fact that the the cover of this book says it’s a sequel to Old Man’s War and The Ghost Brigades already gives away certain information about the plot, let alone the back cover summary. All that aside, I will try to just give the bare bones of this plot along with this statement of the trilogy – it’s a fun, entertaining, and satisfying series. Now, to The Last Colony. 
This novel comes in at over 300 pages but was a quick and entertaining read. The Colonial Union, in classic action movie fashion, brings some hardcore military legends out of retirement for One Last Mission. This time, though, the glory isn’t on the battlefield but in the soul-crushing and mundane monotony of civil service. The legends are charged with helping to install a new human colony on a hospitable planet out amongst the stars. Why the military leaders for the role? Because other alien races aren’t too keen on human expansion. While the planet is hospitable for human live, the political climate may not be. The legends agree to One Last Mission, but quickly find that civil service life includes its own minefields. They have to navigate treacherous political waters amongst the various factions looking to join the colony, not to mention Colonial Union politics and, of course, actually creating a colony.
The book works for a lot of reasons – it’s smart and expansive without being as serious or Very Important as Dune or Foundation. Since it’s the third part of a trilogy, at least some of the characters are old friends by now. The reader is invested in their lives and fates. Plus, Scalzi is great at writing funny lines without dissolving the story into a quip-fest (I think he is less good at walking that line in other series.)
If you read Old Man’s War and enjoyed it, finish out the trilogy! I haven’t read the other books in the series, though, so I can’t vouch for those. I believe there are six total.
