I enjoyed Knives Out, which is an amusing send up of Agatha Christie-style mysteries... Blanc reveals his conclusions before gathered police/suspects at the end a la Hercule Poirot. The film also references other murder mysteries: Blanc quotes Sherlock Holmes, one of the police officers comments that Harlan "practically lived in a Clue board," and at one point, an episode of Murder, She Wrote is playing on a television screen. The plot is smart and cynical; Rian Johnson did a good job writing/directing which, considering the unhinged mess which was The Last Jedi, surprised me pleasantly. There's some contemporary political commentary in the film- apparently it's no longer possible to make movies without it- but it's not overly intrusive or obnoxious. And, unlike in The Last Jedi, it's not so nauseatingly virtue signalling that it becomes cringe-inducing; Knives Out makes it clear that, no matter which side of the political divide the family members fall on, they're all terrible people.
As I said, I had fun watching Knives Out, but the expression "all surface, no substance" comes to mind. It's a clever plot with witty dialogue, but nothing ever runs very deep: this is no Gosford Park, which is another manor house murder mystery with a large cast, but one which has layer upon layer of plot, motive, and character. In comparison, Knives Out is a lot more shallow... I liked it but, unlike Gosford Park, I can't really see myself watching it multiple times. Which isn't to say that it's not an enjoyable film, because it is, but it's what you see on the surface- a fun plot full of twists and turns, amusing dialogue, and a good cast, all of whom seemed to be having a whale of a time making the movie. In conclusion, I recommend watching Knives Out if you enjoy smart, well-paced mysteries... just don't expect too much from it.