I really liked "Luna" by Julie Anne Peters. The featured couple is straight but the girl's sister is trans and that's kind of the focus of the book, even though Luna isn't the main character.

Lauren Myracle's "Kissing Kate" is about a first kiss shared between girls. I didn't like it, but you might. The main character kisses her best friend Kate, but then Kate won't have anything to do with her. It's about the main character realizing her sexuality and losing her best friend. It was depressing to me but I know some people enjoy the angst.

Those are both young adult, modern day type books. If you're willing to go out on a limb, one of my absolute favorite books is "Biting the Sun" by Tanith Lee. It's not about being LGBT specifically, but it's a sci fi that takes place in a world where people are nothing but their consciousness, and bodies can be anything you want. So people often change from male to female and back. The main character feels predominantly female but she is restless and frequently commits suicide to try other bodies out (which isn't illegal, but very frustrating to the machines who see to humanity's comfort). She constantly goes against the grain, and is particularly violent as a male, but ever constant is a close friend of hers who is secretly in love with her. He takes on all kinds of disgusting forms that aren't even human, hoping she will fall in love with who he is, and not how he looks. In the end she is banished for her antics, which are seen as disruptive to society, and he chooses banishment with her and she finally realizes what was in front of her the whole time. They end up a straight couple, just so you know, but the journey is still beautiful and that author plays with gender a lot like that in her other works, including the Books of Paradys series.

"Wraitthu" by Storm Constantine is a fantasy series you may like. I haven't read it in a very long time and I will warn you that it's very...lofty? Intangible? It was a difficult read. From what I recall the race featured is supposed to be genderless but they all use male pronouns and I think the main character and his lover are essentially teenage boys. It was fairly sexual in nature but everything is written in a kind of vague and flowery way.

I'll stop there. lol I really want to read more LGBT works, too, but it's either a bit too juvenile or so hard-core it's just plotless erotica. I want to find some middle ground.