A surprising success! "Why Didn't They Ask Evans" is a real romper of a detective story, packed full of amateur sleuths, red herrings, and clever hints. Particularly well written is the developing relationship between the two protagonists, Frankie and Bobbie. Christie, for all her failings, always manages to write romances charmingly and she does not disappoint here: I found myself rooting for the pair of them to get together the whole way through.
All things considered, this is classic Christie stuff, and probably deserves to be more widely-read than I suspect it is. Even leaving aside the romance, the mystery is intriguing and original, and I was honestly kept guessing until the very end. Furthermore, unlike some of her novels, little clues are dropped here and there regarding the villain's inconsistency in his story, so that the reader can do some sleuthing along with Frankie and Bobbie. The identity of Evans, as the other reader points out, isn't really something that can be deducted, which is slightly disappointing - however, the book isn't really *about* discovering Evans' identity. It is someone who the reader meets along the way, so keep an open mind if you want to have a guess!
The story does take a turn for the bizarre three-quarters of the way through: the heroes are kidnapped and the story becomes slightly more implausible from that point on. This criticism is minor, however; really, the book is Christie at her absolute finest. It is witty, clever, and the plot twists and turns throughout. Fully recommended.