I read this as a child, and loved it then. Now, as an adult, when I read it I recognise all the little touches the author included to keep both audiences happy. The humour is quite dry, even dead pan, the turn of phrase restrained, but the resulting story of Stanley, flattened by his fallen bulletin board and forced to approach life in a new way, is one of the funniest children's books I've ever read.
I'm not sure why the publishers have dropped the original Tomi Ungerer illustrations - I thought they were great, and beware the disappointing abridged version which misses out some of the best bits - but this edition of Flat Stanley still deserves top marks.