This book is part of the author's "Nature Books For Children" series (three books), which is probably the best indication of its target audience and subject matter.

The book is fun and charming, even for adults. Arthur Michell Ransome was an English author and journalist who had a reputation as one of the best English writers of children's books. "This is a book about the things that are jolly and wet: streams, and ponds, and ditches, and all the things that swim and wriggle in them. I wonder if you like them as much as they are liked by the Imp and the Elf? You know all about the Imp and the Elf, do you not?

Those two small jolly children, who live in a little grey house in a green garden, and know the country and all the things in it, almost as well as they know each other? The Imp and the Elf love everything that is wet. They paddle in the streams, and build dams, and make waterfalls, and harbours, and sail boats, and do all the other things that every sensible person wants to do." - Author's description and david wales