My elementary-aged son and I both love this classic book by Roald Dahl. It is a hilarious, slightly perverse (as is characteristic of Roald Dahl) book about a boy getting revenge on his cranky, and decidedly witchy grandmother, by mixing her up a big bubbling potion of medicine which he hopes will turn her into a nicer person (or at least shake her up a bit). The pleasure is both in the mixing of the long list of ever more ridiculous household items, the plotting, and in the rather surprising results! Wonderful, whimsical, if slightly dark illustrations and brilliant use of language.
Its a book that merits being read many times.