Judith Butler's 1990 "Gender Trouble" was widely acclaimed as a groundbreaking book due to its revolutionary ideas regarding gender identity and the relations between gender and sex and the introduction of the notion of gender as performance or gender performativity.
In "Gender Trouble" Judith Butler undermines the distinction between sex as a natural given category and gender as an acquired cultural- social category. Butler argues that sex also is a socially constructed category which stems out of social and cultural practices and in the context of a discourse that has a history and its own social and political dynamics.
In "Gender Trouble" Judith Butler develops her famous performative theory of gender (and the analysis of drag queens in this respect) which tries to account the manner in which a subject identity is formed while establishing Butler's claim that gender identity is not a manifestation of intrinsic essence but rather the product of actions and behaviors, that is, performance. In other words, Judith Butler argues that everyday actions, speech utterances, gestures and representations, dress codes and behaviors as well as certain prohibitions and taboos all work to produce what is perceived as an essential masculine of feminine identity. Butler aims at deconstructing this notion of integrated, stable identity as the extension of an inner essence, and the illusion of the sexual body, which are in Butler's view repressive and dangerous, but also undermineable.
Judith Butler relies in "Gender Trouble" on Michel Foucault's theory presented in "Discipline and Punish", which challenges the relations of body and soul. Foucault argued that oppression imposed on prisoners is not internalized but is rather imprinted or marked on their bodies. Methods of discipline and punishment act on the body and form the image of the recalcitrant inner soul. This image regulates and justifies the actions of power upon the body. Foucault's argument, adopted by Judith Butler, is that the soul is the prison of the body, and not the other way around as was widely held in western culture. In this Foucault means to argue that discourse formations that deal with the human soul and define it essentially operate through the body and on the body, shaping it and marking it with the traces of the alleged "soul" which hides somewhere deep inside. In "Gender Trouble" Judith Butler genders Foucault's notions and holds that gender is in fact the predominant cultural agent which operates on the body, thus constituting the concepts of masculinity/femininity and the identities of heterosexuality/homosexuality. Judith Butler's agenda in "Gender Trouble" is to deconstruct the essential nature of gender identity and to expose it as the fabrication that it is.
Here you can find a detailed summary of chapter 1 from Butler's Gender Trouble.
Additional books by Butler to check out: