This is the third book in the series that started with Old Man's War and continued in The Ghost Brigades. There are a few things that wouldn't really make sense without reading the earlier books.
This is a fast paced adventure story, with plenty of tension, explosions, and good comic relief. Some of the plot is contrived enough to be a bit of a stretch, especially to the extent where some of the odder twists and turns are actually mostly planned. People certainly aren't above such crazy long-range schemes, but they don't really work that well. Underlying the running around and exploding, there are a lot of threads of interesting things to think about, about how governments control people, and about what it means to be human in a universe with other people. It's a bit painful, because I have my own feelings about how I'd like the world to be, and Scalzi, realistically but depressingly, shows us that humans are not likely to go along with it. In one thread of the story, he seems to be working up to the idea that species isn't terribly important to what makes us people, and then on another thread he seems to undercut that with the notion that people have to be fully human (in a genetic sense) to have the right to be fully part of society (or perhaps it would be better to say that the genetically-human people aren't going to accept people who aren't genetically fully human as their equals. We slightly meet one very interesting alien species, and then we don't see them again for the rest of the book, since they don't figure in the main line of the plot. I'd like to see how they turn out, which could be a whole nother book, only slightly connected to the series. It's the way the story ends, though, that leaves me a little cold. It's fine in terms of the historically significant events, but it's kind of a let down in personal terms for the protagonist. I didn't like it quite as much as the first two.
7 out of 10.
**** PLOT SUMMARY -- MASSIVE SPOILERS ****
John, Jane, and adopted daughter Zoe have happily settled down as colonists on the world Huckleberry when General Szilard comes calling. He wants them to be the leaders of a new colony. All the previous human colonies have been founded with colonists from Earth (who don't know anything about the rest of the galaxy, thanks to Colonial Union information control), but they've finally agreed to allow some of the bigger, more established colonies to start one. John and Jane agree to be drafted. Their first obstacle is the fact that this colony appears to have been a pawn in a petty political struggle within the CU administration. The colonies having their own colonies was an idea pushed hard by Manfred Trujillo, but when it finally gets approved, instead of being the leader (as he thinks he should have been), and the whole population coming from one world (his), it has people from ten different worlds and outsiders for leaders. At this point, Man is a conniving prick of a politician and he and John hate each other. There's also the self-aggrandizing tabloid reporter, and the delegation of Mennonites, whom everyone else expects to be a burden on the colony. And then the leaders learn about the Conclave, a federation of over 400 races who are trying an experiment unprecedented in galactic history, to wit getting together in a group instead of shooting at each other. The CU opted out of this enterprise and is actively trying to sabotage it. The Conclave, however, refused to fall apart despite the CU's plans, and has decreed that no new colonies are to be founded except by the Conclave on their terms. Roanoke, as the new colony is to be called, is in defiance. The CU allows them to see a brief video of the assembled Conclave fleet utterly destroying another defiant colony.
Then the ship skips, there are a couple of glitches, and they figure out that the world they're on isn't the one they thought they were going to. Stross, a Gameron -- one of the space-adapted Special Forces guys we met in the last book -- shows up and explains that this world is where they will really be putting their colony, and they'll be doing it without any modern technology so that there won't be any radio signals to help the Conclave find them. This is why there was all that weird extra stuff in the cargo manifests. Also, the ship's crew are going to join the colony, and the ship is going to be dumped into the sun. All concerned are displeased with this, but Stross says that he's in control of all the ship's systems, not just the engines -- if they don't agree he'll cut off life support. So they go along with it. There are a couple of other surprises in here too. One is that Szilard slipped Jane a nanotech mickey which upgraded her normal-human body back to a Special Forces soldier (minus the green skin, but with the superior strength and speed and a new BrainPal. The other is that the video they'd been given of the colony being blown up was edited; the full one shows General Gau meeting the leader of the doomed colony, a former friend, and trying to get him to agree to either join the Conclave or to be shipped offworld. The colony votes and refuses, and only then do they get fried by the Conclave fleet. The Roanokans set up their colony. There are some glitches, but it basically goes well. They discover that the planet has a race of primitive tool-users there already. There's a little bit of interaction with them, and then we don't see them again as the plot unfolds. The CU comes back and imperiously tells the Roanokans that they are no longer in hiding. The colony ship's crew is allowed to go home, and the colonists are allowed to start using tech again. Shortly, right on schedule, General Gau shows up and gives the colony three choices: join the Conclave on their own, be repatriated, or be killed. John offers to accept Gau's surrender, and then tells him to leave, but it appears to just be banter, and Gau of course doesn't. The big fleet shows up, and then all the ships in the formation blow up. It seems that Gamerons had infiltrated all of the Conclave worlds and placed antimatter bombs on all of the ships except Gau's.
The CU's master plan goes a little off course from here. This was supposed to precipitate a civil war which would put paid to the Conclave once and for all. There is a big rift in the Conclave, but unfortunately, the one thing they all still agree on is that the humans need to die. The war is starting to go badly for humans. When John is summoned to an inquiry about how he tried to tip Gau off, he learns that Roanoke is being used as a pawn again. When it is destroyed, the CU figures it will be a rallying cry to support a massive recruiting drive among the colonies, who up to now have not provided soldiers (they all come from Earth, except for Special Forces who they make themselves). General Szilard's own analysis is that the Conclave will respond to this military buildup with a push to completely eliminate humanity, but he's not in charge. So he's doing what he can, by giving John the task of trying to find a way out. They have some conveniently vague intelligence that there is a plot on General Gau's life. John calls in a favor from the Obin, the aliens who worship his daughter, and they take Zoe to deliver the message to Gau. Gau gets the message, survives, and is mostly back in control, but there is one faction, led by Eser, who is still up for killing all of us monkeys. Luckily, he's more of an egomaniac than a soldier, and he has a crazy plan to eliminate Roanoke with a small ground force rather than aerial bombardment. The Obin bring a god-tech surprise gift from the Consu which makes the invader's guns blow up in their faces, and that and Jane's powers allow them to wipe out the invaders and send Eser off for trial.
John and General Gau hatch a new plan for the Conclave. They break the information blockade on Earth and let the population know the truth about the Conclave. The CU, however, isn't too pleased with John and Jane; they have been removed from their leadership role and settled back on Earth. The final big surprise is that Szilard reveals that Jane's body (the one she's had for the whole book) is actually genetically 100% human; the enhancements have been nanotech only, not in the DNA. This is supposed to be a big step in getting the rest of humanity to accept Special Forces soldiers as real humans. Only Jane already knew it, because she's pregnant.