No Spoilers except: meh.

I’m a HUGE Agatha Christie fan. HUGE. I’ve been reading her mystery novels for over 30 years; they were among the first Grown Up novels I read as a kid and are the basis for my love of mystery novels and tv procedurals. I have read and watched every Poirot and Miss Marple book, movie, episode. So imagine my shock and glee when I discovered that there was an upcoming movie, starring my beloved Gillian Anderson, of a Christie novel that I could not remember reading!
So, I went in to this book humming *Everything is AWESOME*, to be clear. There is a foreward from the Dame herself describing this story as one of her special favourites. She tells us that she saved up the story and characters as a treat to herself to write when she really wanted to enjoy herself. If this isn’t a clear example of an author not understanding the appeal of her own work, well, I don’t know what is.
Spoiler Alert: This book is the most meh thing I’ve read in a very long time. I can’t even say that my expectations were too high– like I said, I’m a fan. I know what I’m getting in a Christie novel. All the usual stuff was there: murder, poison, money troubles, secret affairs, missing will, upper class family, servants, Scotland Yard, etc. But the sum total of all those things was so boring and unfocused and uninteresting. It was as if Christie forgot how a Christie novel works, and not in a genre-defying clever plot twist way.
The narrator of the book is Charles Hayward, who is in love with Sophia Leonides. Her mega- rich grandfather is murdered in the family home, by a member of his extended and eccentric family. He has a new beautiful young wife, 2 ne’er-do-well sons, grandchildren, various retainers and hangers-on. Someone within his household killed him, but it’s almost impossible to tell who because they all had equal opportunity, so the whole family lives under the shadow of suspicion.
Sophia refuses to marry Charles until the murder is solved. Fortunately, Charles’s father just happens to be the Assistant Commissioner of Scotland Yard (what a clever plot contrivance) so Charles is able to get the inside track through Sophia to help solve the crime. Except… he doesn’t? Charles is practically non-existent as an actual character. He observes, narrates, is easily and foolishly manipulated, and in the end makes no contribution to the solution of the crime. In fact, no one really solves the crime. It’s just explained and neatly wrapped up in a letter. The End. meh.
There is no Great Detective or final reveal in this Agatha Christie novel. The closest to a detective is the youngest grandchild Josephine, who is an unbelievably unappealing little plot moppet. Christie was always better at writing dogs as characters than children, but in this case, holy blue. Not all children are either precious lambs or creepy sociopaths, Agatha.
I can see why this is one of the few Agatha Christie novels that has never been filmed. It’s not her best work and the solution would be tricky to do well or dramatically. I’m still interested to watch the film, tho. Because Gillian Anderson!