The story of the The Gremlins concerns the mischievous mythical creatures of the title, often invoked by Royal Air Force pilots as an explanation of mechanical troubles and mishaps. In Dahl's book, the gremlins' motivation for sabotaging British aircraft is revenge of the destruction of their forest home, which was razed to make way for an aircraft factory. The principal character in the book, Gus, has his Hawker Hurricane fighter destroyed over the English Channel by a gremlin, but is able to convince the gremlins as they parachute into the water that they should join forces against a common enemy, Hitler and the Nazis, rather than fight each other.
With full-page color illustrations and with several black and white illustrations by the Disney artists throughout.

This was Roald Dahl's first book and preceded the British publication by several months. The story was optioned by Disney and was intended to be made into an animated film, but it was never produced. A note on the copyright page states: "The RAF Benevolent Fund will receive the author's share of the proceeds from the sale of this book." Dahl's next children's book, James and the Giant Peach, published eighteen years later.