The book is meant to be read more like a novel than a traditional textbook or non-fiction book. The CS Detective centers around the story of a disgraced ex-detective as he tries to unravel a mystery. The computational concepts are acted out in the chapters (to provide real world motivation) before being explained in more detail in the following technical section. Those technical sections are optional to the story, but provide the best explanations of the computer science concepts.
Campbell Ritchie wrote:How many other CS detective books are there?
It depends on how you look at it. This is the first CS Detective book in terms of the main characters and using the detective genre. The other two books you mentioned are part of the same world though. Like The CS Detective, they explain different computer science concepts through amusing stories. Chronologically they occur before the events of the CS Detective and some of the minor characters, locations, etc. appear across the books.