I've never before read anything by Christie, and I was expecting to be bemused by a period piece.
Instead, I was enthralled, unable to put down the book until I had finished. Not only that : since I'd never seen the movie, I was depending on the book alone , and I was utterly amazed by the ending. I never saw it coming. Great fun!
(One cavil: anyone who reads this should be prepared for some musty, unpleasant cultural stereotypes. This book is not politically correct... but one must take it as a period piece, after all.)