Wonderful.
5 stars
I think I like this book even more than the others in this series, which are also books that I adore. This one has a bit of a clever solution, even if some of the clues start lining up a bit early. If you're not reading it to solve it, it's not going to be overtly obvious what's happening and what machinations are taking place.
I also found that there were a lot of interesting philosophical conversations taking place, which I found quite interesting. They weren't overly long or verbose, and they also fit quite neatly into the narrative without bogging it down. Each of them felt exactly like how someone thinking of a problem would vocalise their random thoughts.