This is not a fairy tale. This is about real witches." So begins one of Roald Dahl's best books ever, and, ironically, it is such a great story because the premise is perfectly plausible from the outset. When the narrator's parents die in a car crash on page two (contrast this terribly real demise with that of James's parents who are devoured by an escaped rhinoceros in James and the Giant Peach), he is taken in by his cigar-smoking Norwegian grandmother, who has learned a storyteller's respect for witches and is wise to their ways.
The bond between the boy and his grandmother becomes the centrepiece of the tale--a partnership of love and understanding that survives even the boy's unfortunate transformation into a mouse. And once the two have teamed up to outwitch the witches, the boy's declaration that he's glad he's a mouse because he will now live only as long as his grandmother is far more poignant than eerie.

Of course, there's adventure here along with Dahl's trademark cleverness and sense of the grotesque. Dahl also communicates some essential truths to children: if they smoke cigars, they'll never catch cold, and, most importantly, they should never bathe, because a clean child is far, far easier for a witch to smell than a dirty one.