Watch Your Mouth is a novel by Daniel Handler, which he has described as an “opera in book form”, about Joseph, a young student staying at the home of his girlfriend, Cynthia Glass, one summer. The first part of the novel is laid out as an opera, each of the characters being assigned a singing voice. Joseph quickly discovers that Cynthia's family is unusual, not to say bizarre, with interests ranging from incest to the Kabbalah. Aside from the (off-stage) sexual interactions, Cynthia's mother, Mimi, turns out to be building a golem. The first part of the novel ends (operatically) in death. The second part is presented somewhat more conventionally, as Joseph attempts to recover from the events of the first part.

Watch Your Mouth (ISBN: 006093817X) is a black and sexually explicit comedy.