This useful book traces the development of the category of gender identity, which has  become prominent in current popular discourse and is often invoked in legislation or rules. The term first originated in medicine, to denote individuals with rare sex disorders. Feminists in the 1970s used gender to denote patriarchal social structure and culture, in ways far removed from the current focus on gender identity as a general attribute. Gender identity gained prominence in the 1990s with increasing advocacy for medical interventions to align sexed bodies with identities as belonging. This was seen as extension of a general minority rights revolution, which eventually embeds the concepts in institutions and discourse. Although initial proposed reforms generated little attention or controversy, there has been increasing debate and polarization since around 2015, as assertions with reference to gender identity may come into conflict with impacts on others or in tension with other principles such as legislation to protect rights of women based on sex. Brubaker notes that although political conflict over gender identify is often interpreted in a progressive-conservative frame, based on US experiences, this does not fit how opposition to legislation framed around gender identity was often led by traditional feminist and gays in the UK, and how the new emphasis on greater caution in medical interventions appears in the generally liberal Nordic countries. Brubaker insists that he is not interested in what gender identity actually is, but defends the need for ‘sober analysis’ to understand how we have reached ‘our current predicament and how we might move forward’, against the background of the Trump administration’s radical policy change and rhetorical assault on gender.