I started reading Christie approximately a year ago. I've read perhaps 30 of her works, to date. I suppose I could have started a discussion focussing on "Favourite Novels", but the difference between "favourites" and "least favourites" is similar to the idea expressed in the first line of Anna Karenina: "Happy families are all alike; every unhappy family is unhappy in its own way." It is so rare that I am truly bewildered and disappointed at the end of a Christie book, that I want to bring attention to this unique experience.
My least favourite Christie book is "Passenger to Frankfurt".
It seemed that 80% of the book was taken-up in repeating the same tirade, again and again: about terrorists trying to bring-about a "new world order". The problem is not with the theme: I thoroughly enjoyed "The Big Four", which has a similar theme. The problem is that I actually had the instinct to skip complete paragraphs and even complete pages, because I knew exactly what they would contain: another long description of the horrors about to befall us, should our heroes not solve the mystery at-hand. But although my patience was stretched to breaking-point, I did NOT skip any paragraphs: I stuck with the book, hoping for a reward, in the end. When it was all over, however... I was still disappointed. "Bewildered", as I say, is a better description. I revere Christie, but really don't know what the "point" of this novel was.
Many of her novels and stories have a "solution" at the end which could be (perhaps only after you've read 30 of them, in quick succession?) described as anti-climactic: the murderer is not someone we cared about very much; they're a minor character; the many mysteries which have been niggling at us throughout the book don't come-together in one brilliant flash: but I still ENJOYED THE BOOK. This is the main reason I name "Passenger to Frankfurt" as my least-favourite of her books: it was both anti-climactic, and also incredibly laboursome to get through.