Perhaps the best of the books I have read by Roald Dahl. It is phenomenally well written book about a five year old genius. Dahl knows exactly how to write for children, which is mostly the same as you would write for adults. It is very well written. The characters are Dickensian stereotypes and, interestingly, various books by Dickens are referenced in the book. The villains are especially villainous and the book moves from brilliant set piece to brilliant set piece. The villainous headmistress, Trenchbull is especially well done and the pieces with her sing.
Dahl is an interesting author, and the world that he paints is one of inherent danger. For instance, in this book, Matilda's parents are terrible parents and Matilda is openly opposed to them. That is very brave for children's literature. Dahl pretty much tackles whatever he wants, using any word or sentence he wants, and has a consistently dark world view, although it is a wold view in which good does eventually beat evil. Dahl also has this pervasive tendency to conflate a persons aesthetic values with their moral character which makes for brilliant catty writing. The whole thing is very good and is a near masterpiece. It is marred by an injection of the supernatural at about the two thirds mark, which felt wrong to me. Its that turn in the narrative that stops it from being a five star book.
The illustrations are by Quentin Blake, who is also almost a genius. His pictures are expressive and delightful.
Overall an excellent book and shows that Dahl was one of the best children's writers in history. People should write children's books like this and not in the terrible, gutless, patronizing way that they are usually written.