All Poirot novels
Cat Among The Pigeons.
, what is unique about this particular Poirot book is that it combines both mystery (whodunit) and spy thriller which results in a different kind of Poirot. Right from the first page, Christie pulls the reader in and never lets go. Just a few weeks ago I listened to an audiobook (abridged) of Cat Among the Pigeons and listened to the beginning and it just grabs and pulls you right in, way before Poirot comes in, way before we are introduced to the all-girls school Meadowbrook.
Finished this last night. A good, fun novel IMO. Have to pitch in on the knee thing. I believe, rightly or wrongly, that Poirot has had ample experience of women during his youth back in Belgium before the war. After all, when we first meet him in Stiles he's got to be, what, about 40 at least (maybe someone has a definitive answer to his age), plenty of time to gain experience and then settle into a more sedate attitude.