One could say it was an academic exercise on Christie’s behalf, to pen a Poirot tale in which he solves everything from his apartment, or perhaps it started off as something else, and she opted to insert Poirot in it, just to show that Poirot could still deduce without investigating. (He is, quite literally, an armchair detective here.)
I wouldn’t recommend it to anyone but the biggest Christie fans, but there is a lot in it for those willing to pick it up: the town is lushly built out, the espionage details are deftly — albeit stodgily — handled, but most importantly: she — via Poirot, of course — opines quite a bit on the history of detective fiction, and weaves quite a bit of her favorite trappings it into the tale. While reading it, I fully realized I was missing out on about half of the neatly dropped references.
Again, only for the hardcore, but I found it both intriguing and illuminating.
I have two more Poirot novels left to read: THIRD GIRL and ELEPHANTS CAN REMEMBER, but I plan to cap this seven-year endeavor off with a re-read of the ‘final’ Poirot novel, CURTAIN.