Start with high-confidence gay studies books, then narrow by subgenre or adjacent topics.
The Struggle Over Gay, Lesbian, and Bisexual Rights
Kimberly B. Dugan
Creating a Place for Ourselves
Brett Beemyn
Close to the Knives
David Wojnarowicz
Queer Studies
Brett Beemyn, Michele Eliason
Positive Images
Dion Kagan, Angela Smith
Go the Way Your Blood Beats
Michael Amherst