As a born-and-bred Czech, I found the book quite informative and funny. I learned quite a few things and, and there are some fantastic insights.
However, I was surprised by how much information in the book is plain wrong, how many inaccuracies there were, and how much stuff was true maybe 20+ years ago, although it was first released in 2008. For example, Czechs attend dancing classes in the second year of high school, not the last, celebrating name days is not a bigger deal than celebrating birthdays, the word "robot" was coined not by Karel Čapek, but his brother Josef, the word "brk" is never used to mean "penis", and many others.
Generally, I recommend this book to native Czechs who want to gain a new perspective on their country. Also, foreigners living or thinking of living in the Czech Republic will certainly find the book useful, but I suppose it goes without saying you need to take such books with a grain of salt.