Yes, it is well-written detective story. Yes, it's hard to get in as and as we advance in his reading. However, Fred Vargas had accustomed us to better in his intrigues. It's a bit twisted, and above all, the strings used are too large: a queen MEMEE hacking and Robin Hood of modern times, outputs are not sure where; or a change of identity is easy on landing in 1944 ... The only really interesting is the way in which the character is dealt Adamsberg, who is pushed into a corner as ever, responding in entirely new ways.
