Both women characters, Emma and Lucy, are very likable, each in their own way.
I enjoy the idea of Lucy being a 20th century Marie Kondo with an Oxford Maths Starred First: there must still be people like her to help the super-rich enjoy their riches.
The book is also a reminder on how modern Agatha Christie was. Even though there were still (some) porters at her train stations, there were already broadcast systems with impersonal voices announcing times for trains.