As with most of the British Library Crime Classics, this is very readable and entertaining for what it is: a piece of Golden Age crime fiction by a competent writer, with the usual sort of mystery with a solid policeman methodically tracking down whodunnit. I don’t read these reissues because I’m expecting a forgotten masterpiece, so I wasn’t disappointed!
The Body in the Dumb River deals with the death by stabbing of a man who travels around Britain working a hoop-la stall. His assistant and lover must be questioned (in a rather sympathetic scene, without drama), and so must his wife and children — for whom the idea of him running a hoop-la stall is a pretty distasteful surprise. The scenes with his actual family are rather less sympathetic: the murdered man was henpecked, driven to distraction by his indolent, lazy wife, and his wife’s family are all pretty unpleasant.
As I said, it doesn’t stand out above the crowd, but it was a quick and enjoyable read for what it is.