Books with gay characters are more available now although the offerings are still somewhat sparse. Nonfiction books on gay issues are even harder to find. The Stonewall Awards from ALA's GLBT Round Table, first given in 1971, include fiction and non-fiction for adults, young adults, and children. You can find them here: Stonewall Book Awards
More are fiction than nonfiction, but a powerful nonfiction book that won a 2014 Stonewall Honor Award is Branded by the Pink Triangle by Ken Setterington (Second Story Press, 2013; 155 pages.
The author, a well-known librarian and writer (and a friend with whom I served on the Newbery Committee), tackles the hard subject of the Nazi persecution of gays, especially men. He relates heartbreaking stories and gives grim statistics of incarceration and death. Berlin had a surprisingly open gay community before the rise of Hitler, making the change all the more shocking. Gay men were forced to wear pink triangles, the counterpart to Jews wearing yellow stars. Then after the war, those who survived were not free to tell their stories in a world where homosexuality was typically illegal. While acknowledging how much things have changed for the better, Setterington also reminds readers that in some countries, homosexuality is still outlawed and gays are openly persecuted.
This is a highly readable, must-have book for middle schools and high schools to introduce students to one more aspect of the Holocaust that we should never forget.