The story revolves round a diamond called The Moonstone, stolen from its native India by John Herncastle. The Moonstone was believed to bring bad luck to its owner, so Sir John gave it to the daughter of his estranged sister, Rachel Verinder, on her eighteenth birthday.
On Rachel's birthday, it is discovered that the jewel has been stolen from Rachel's sitting room. Sergeant Cuff is called in from London to investigate.
The book was written as a series of manuscripts, letters and diary extracts from the main characters present at varying parts of the story. Perhaps because the characters were telling the story almost as if they were talking, the language was very easy to understand. The characters are beautifully portrayed and the format of the book only exacerbated this.
The key to the story, although a fascinating idea, isn't quite as believable as it could be. To a reader of the time, it probably wasn't beyond the realms of imagination; to a reader of today, with our knowledge, it is. This is the only disappointing part of the book; but even that, it does mean that it is even more difficult to guess how the theft was carried out and by whom.
All in all, this was a really enjoyable book.