Scalzi is going to be one of those authors who you would like to listen to as an audio book but not to read. Looking through several reviews he does do a lot of he said, she said and now that I know it I can't unsee it. And I get where it can get annoying. I also enjoy the humour.
Plot: It has been several decades since Earth had first contact and now Earth has become something of a tourist destination. After a diplomatic mess one of Earth's allies demand that the Earth government get a sheep for their sacrifice. This specific sheep species soon goes extinct. Enter Harry Creek who has to find out who is sabotaging Earth relations, and find just one sheep. Many different factions try to interfere, secretly help, or just add to the world building.
Characters: Harry Creek is the basic hero archetype. You know the type, feels like he should be wearing a superhero costume and fighting crime, they even gave him a boring government job. John does give him some depth but this guys seems to have it all. Strong, handsome, (I assume), genius levels of intelligence, tragic backstory, military training. Really, you have to try hard to find a flaw.
There are some other character but I feel that if I went into their personalities and back stories it could spoil the plot.
What I like: I like most of this story but once again I do recommend that. I do like the world building and it is fun to see some science fiction where all the aliens aren't evil, they are just dicks. What I don't like: Again that He said, she said, he said. Does get annoying. If you are going to get this book I recommended getting the audiobooks.