As you may have figured out from the whole Queer Scifi/Fantasy Bundle I offer, I'm a big fan of, well, queer science fiction and fantasy. I've got an internal database filled with lesbian necromancers, soft gay dads, bisexual teens in magic school, and Hamlet retellings with trans Horatio. But the fact is, there are some genders and sexualities that are a lot harder to find than others, which is too bad since the pun opportunities are… aces.
Needless to say, as soon as I was made aware of this lack, I hastened to track some good asexual and aromantic stories down. Quick queer vocab lesson for those who need it: people who are asexual don't experience sexual attraction and people who are aromantic don't experience romantic attraction. Like all queer identities, asexuality and aromanticism are spectrums. Some people are one, some people are both, some people do experience sexual or romantic attraction but only rarely, some people are actively repulsed by the idea. Everyone deserves representation, so I've tried to include a good mix.
This is probably one of the better known ace books because Seanan McGuire is well known in both the queer community and the science fiction/fantasy community. Nancy, our protagonist, is asexual, but that's not what drove her to Eleanor West's Home for Wayward Children. That's spending years in a magical world and then being spat back out with no way to return to the world that felt more like home than any other. Her asexuality is important to her as a character, but it's far from what defines her and it isn't the plot.
Alternate history where the Civil War was derailed by the zombie uprising. This book is fantastic for so many reasons, but let's focus on the secondary main character, Kate. While they never use the word, they make it clear that she doesn't experience romantic or sexual attraction at all, and more, that she's comfortable with that. She's got bigger things to worry about. Like zombies and racism. Romance and sex just seem terribly inconvenient.

Sal's sexuality isn't revealed explicitly until the second book, but it's still pretty clear from reading it that he's aromantic. Admittedly, romance would be hard for anyone to focus on when you can tear holes through the multiverse and bring alternate, living versions of your dead mother into your own world. But other people are definitely interested and he'd just rather focus on his magician skills. In Sal and Gabi Fix the Universe, Gabi clears things up completely and says "if you were any more aro, I'd shoot you out of a bow," which is great because it's both explicit representation and a pun.

This is a modern retelling of the Arthur mythos that centers on Rani Arturus after she pulls the sword from the stone. Like any good Arthur, she immediately finds herself a Gwen and a Lancelot, but in this case, the love triangle aspect at least goes a little differently. See, Lance is asexual, though not aromantic, and Gwen is smart enough to make everyone talk about their feelings and work out how to make them work as a romantic triad. Now all they have to worry about are the rampaging fae that want to destroy the world! Easy.

I tried not to include too many robots here, but I'll make an exception for Murderbot. The universe Murderbot inhabits is so enthusiastically and openly queer, and Murderbot is so human (though it would be offended if you said so to its face) that its asexuality never comes off as a robot thing, more a thing that is specific to Murderbot. It loves overwrought soap operas but fastforwards through the sex scenes. It develops feelings despite its best efforts and keeps making friends but certainly not romantic or sexual partners. Just people it has to keep from dying no matter how stupid the choices they make are.
I'm still reading this one, so no spoilers!! But Ellie, the titular character, is explicitly uninterested in dating and plans never to get married. What she is interested in is her ghost dog, Kirby, that she raised from the dead using secrets passed down through the line of her Lipan Apache family. She's also interested in solving her cousin's murder, which was definitely not a car crash no matter what the authorities believe.