If you needed a clue that Stephen Baxter, well known exponent of hard sci-fi, where he surely has to explain the most esoteric science fiction creations, has jumped genre to write for a younger audience, it's surely in the foreword, where he details pre-decimal coinage. What follows doesn't need much explanation, as it's all written with a great clarity. I'm sure someone will want to film this for TV or the cinemas, and it's almost directed for you already, so evocative is the simple yet compelling writing.