The Moonstone is a very early example of the Mystery genre. It has a complicated series of interwoven plots. These are made even more difficult to predict and navigate through Collins's use of misleading clues, false assumptions presented as facts, and red herrings (things which seem like clues but which are really intended to be misleading or distracting, like Rosanna's replacing of Blake's stained nightgown). There's a moral component to truth-telling in novels like this, and characters who lie about serious matters are often depicted as being villainous. The Moonstone's plot needed to be both intense and dense in this way because the novel was originally published as a serial in the journal All The Year Round. Collins needed to keep readers interested in the storyline, so many sections of the novel end with startling revelations or cliffhangers.
Because the novel's mystery is diffused through this in a series of letters and "reports," The Moonstone also belongs to the Epistolary genre—novels that take the form of a group of related letters. As with many epistolary novels, The Moonstone also belongs to the genre of Realism. The sequential nature, emotional frankness, and detail of the letters in the book represent Victorian life in a detailed and careful way, incorporating contemporary issues and local color into the narrative.
The Moonstone is also widely considered to be the first British novel in the Detective Fiction genre, sometimes also called the "whodunit." In this kind of literature, a figure appears whose job it is to cleverly and patiently seek the truth after a crime has been committed, often in difficult circumstances. The Moonstone actually has two "detective" figures: the useless Seegrave, who just harangues people, and the clever and heroic Sergeant Cuff.
This novel also belongs to the genre of Sensation fiction, which are Victorian novels intended to evoke extreme emotions in the reader. Sensation fiction was very popular from the 1860s to the mid-1880s, as it combined elements of two of the most popular kinds of fiction being written at the time: realism and romance. Books in this genre are characterized by the presence of one or more important secrets, which the plot usually reveals bit by bit. Sensation fiction also contains extreme and dramatic ups and downs of plot; shocking subject matter including murder, theft, death, affairs, premarital sex; and scary or macabre influences from the Gothic genre of literature. Notably, Collins's fifth published novel, The Woman in White, is often cited as the first popular example of this genre in English Literature.
