Margery Allingham's detective Albert Campion is not really very appealing. His decision to pretend to be stupid might be useful for the process of detection, but it doesn't make for a very pleasant reading experience.
In this mystery, Albert is trying to protect an American judge from the murderous intentions of the dangerous Simister gang. Nevermind that we don't really know much at all about the Simister gang aside from the brief mention in The Crime at Black Dudley. Suffice it to say that they are apparently very sinister and very dangerous. The American judge is clever but curmudgeony. His son is dashing and worried. His daughter is very beautiful and cries all the time. Albert's young friends with whom he secrets the judge are young, dashing, and worried, but in a much more British way. There is also a clueless art dealer, some colorful local people, and a chatty sneak thief. The characters are mostly entertaining, and I particularly liked Albert's friend Biddy and his large, criminally-inclined manservant, Lugg. Unfortunately, I didn't like Albert himself, which makes reading book in which he is the main character rather difficult.
The mystery itself was all right, and the plot moved along at a reasonable clip. At the end, when Albert stopped pretending to be an idiot and actually let his true self shine through, I finally really got into it. Too bad it took so long for that to happen.
This is definitely in the vein of Agatha Christie or Dorothy Sayers. I'm told that the books get better as the series continues, but it may be a while before I make another attempt.