It is very difficult to classify THE MAN WHO WAS THURSDAY. It is possible to say that it is a gripping adventure story of murderous criminals and brilliant policemen; but it was to be expected that the author of the Father Brown stories should tell a detective story like no-one else. On this level, therefore, THE MAN WHO WAS THURSDAY succeeds superbly; if nothing else, it is a magnificent tour-de-force of suspense-writing.