One of the conveniences of resorting to different heroes in different books is that you can have extraordinary things happen to them, all the while maintaining a sort of relative normalcy; "this is a once-in-a-lifetime experience!"
The pitch of this particular French-novel is original, indeed : The detective is faced with a corpse bearing a remarkable resemblance to herself, thus allowing for her to go undercover and assume the victim's identity in order to uncover the killer.
Focusing more on the victim than on the murderer is a new take, and bold moves are regrettably rare in this genre. It is a little sad, therefore, to realise there is actually a reason why investigations tend to zoom in on the perpetrator. It gets a bit boring when nothing happens!
As a result, what ought to have been a pageturner finally turns out to be little more than an OK thriller.
I suppose not even French hits a home-run every time.