Memoirs of Hadrian by Marguerite Yourcenar. Arguably the greatest queer novel of all time. The love affair between Hadrian and Antinous is both wonderful and disturbing. It's pitch perfect, not for a moment does one think it is not written by Hadrian himself.
Yourcenar was a Lesbian, partnered with Grace Flick, yet she had a habit of falling in love with gay men. All her novels, that I know of, have a gay man as the main protagonist.
The Twyborn Affair by Patrick White. One of the greatest mysteries to me is how Patrick White is such a relative unknown in this country, particularly among queers. This was an openly gay man who won the Nobel Prize for literature for crying out loud.
Twyborn is a masterpiece. White is a master stylist, his language is incredibly beautiful. I can recommend many of his novels, but in this one he deals with issues of gender, some 30 yrs before it became popular to do so.
Time Remaining by James McCourt, a mess of a book. I truly believe that McCourt wrote it while on crystal meth or something, but one again, this is pitch perfect. I consider it the best AIDS novel ever.
The story is in two parts, the second of which is told by an older, erudite, drag queen with a keen intelligence, Odette O'Day (yes, he's referencing Proust), as she travels on a train in the middle of the night. A whole world comes to life, everything we lost.
Corydon by André Gide. This book meant the world to me when I was growing up. It consists of Socratic arguments about homosexuality, originally published almost 100 years ago. I believe Gide was the first openly gay man to win a Nobel.
To close, The Body and Its Dangers and Other Stories by Allen Barnett. I love this book because it came out at the height of the AIDS epidemic. He died not too long after. It's a stunning book, both artistically and as a record of the times.
That's all for now. It's only five books (If I were to add a lesbian book, my favorite these days is Aquamarine by Carol Anshaw). As I said, this is only a list of books that I think don't get enough attention. I always feel guilty about recommending books on Twitter.
And I forgot to mention one of my favorite queer novels, a masterwork, A Book of Memories by Péter Nádas. It's a big novel, Proustian. Difficult to get into at first. Susan Sontag called it "the greatest novel written in our time, and one of the great books of the century."