Okay, this is more like 3.895674 stars, or something.
The Android's Dream, a knowing reference to Philip K. Dick even in the novel, takes place in a version of the near/distant future where Earth is part of an interstellar alliance known as the Common Confederation, and aliens are just everyday business to the citizens of Earth (also known as the UNE, or United Nations of Earth). A diplomatic crisis is started when two trade negotiators die during negotiations under very strange and suspicious circumstances. The whole thing spirals until the fate of the world depends on finding the last of a very rare and genetically designed brand of sheep, The Android's Dream, which was specifically designed for the monarchy of the Nidu, an alien race that is threatening to enslave the Earth unless they get their sheep, dammit. Things escalate/are revealed from there, and it all makes sense in the end.
There were a lot of things I really liked about this (like Brian, the worlds first second artificial intelligence, and the very weird artificial religion that knows it's an artificial religion, but takes meaning from believing in it anyway), and some things that really weirded me out at first (like Robin being part sheep, and her sheep mother, and the guy who eats people whole, and the fact that Scalzi NOT ONCE confirms whether Sam Berlant was a man or woman), but I came to accept them. I think the problem for me was the tone, which was only sometimes a problem. Sometimes it was serious, sometimes it was ridiculous. Sometimes they were talking about the worst battle in human history and people dying, and sometimes they were talking about killing aliens by farting. (First sentence: "Dirk Moeller didn't know if he could fart his way into a major diplomatic incident. But he was willing to try.") The whole fate of the world depending on a lost sheep thing was a little far for me to stretch at first, but Scalzi makes it plausible in the end.
All together, not my favorite Scalzi book, but good all the same.