Call numbers will help you browse the shelves.
Dewey Decimal Classification
155.3 Sex psychology; psychology of people by gender or sex, by sexual orientation
305.3 People by gender or sex
306.76 Interdisciplinary works on sexual orientation, transgenderism, intersexuality
306.8 Marriage and family
355.0086 LGBTQ+ people in the military
616.89086 Sexual and gender identity
920.0086 Collected biography of LGBTQ+ people