Canonical aro and/or ace

Elatsoe by Darcie Little Badger

Young adult. Elatsoe's America is slightly different from the one we know. Magics and monsters both everyday and dangerous inhabit her world. Elatsoe herself can raise the ghosts of dead animals, a skill passed down through generations of her Lipan Apache family. When her cousin is murdered, Elatsoe decides to find out just what happened, even as his home town does everything it can to bury a truth older and larger than she could've imagined.

Not Even Bones by Rebecca Schaeffer*

Young adult. Nita isn’t a murderer - technically. She just dissects the bodies of supernatural beings her mother brings home and sells for parts on the black market. But when her mother brings home a still living victim, Nita has had enough and frees him. As it turns out, no good deed goes unpunished as Nita is betrayed, her own nature as a supernatural entity outed as she’s kidnapped and placed behind bars. Now she must find a way to escape before she’s sold for parts.

Winter Tide by Ruthanna Emrys*

Aphra and her brother are the only survivors after the government raided their home, Innsmouth. Their only living family are the amphibian people of the deep, whom they will one day join, but until then they are bound to land where they struggle to build new lives for themselves after the great loss of their home and loved ones. Then rumors start to spread of a Russian agent seeking dangerous and ancient magic, forcing Aphra to involve herself as they try to stop it.

All Systems Red by Martha Wells*

After having hacked its own governor module, SecUnit uses its small amount of new freedom to secretly download and watch as much media as it can between doing its job guarding humans. But when the scientists it’s been charged with keeping safe come under attack, it must make a choice about whether to continue keeping its freedom secret or risk it all to save them. I leave up to individual judgment whether SecUnit counts as agender, asexual and aromantic, as it is a robot.

The Angel of the Crows by Katherine Addison*

Sherlock Holmes retelling. After having been injured fighting a war against fallen angels, Doyle returns to London to survive on only a veteran’s pension. To afford a place to live in the city, Doyle finds a housemate in Crow, an eccentric angel with a great curiosity for humans and a knack for solving crime. And London needs its protector - supernatural beings walk the streets, and someone going by the name Jack the Ripper terrifies the citizens at night.

Vicious by V.E. Schwab

While studying near-death experiences as college roommates, Victor and Eli discovered something incredible: under the right circumstances, someone can develop seemingly supernatural abilities. When they moved their research to the experimental stage, things went horribly wrong. Ten years later, Victor has broken out of jail and sets out to hunt his former friend, who is on a mission to eradicate all other superpowered people in existence.

Word of god aro and/or ace

Vespertine by Margaret Rogerson

Young adult fantasy. Artemisia prefers the dead to the living, and is training to become a Gray Sister, a nun who helps the souls of the deceased pass on to the afterlife rather than remain as dangerous spirits. To defend her convent, Artemisia accepts the help of a dangerous revenant, a powerful spirit which grants her great power but also could possess her the moment her guard is lowered. As evil threatens her homeland, Artemisia and the revenant must find a way to work together.

Archivist Wasp by Nicole Kornher-Stace

Wasp is the chosen Archivist in a post-apocalyptic world haunted by the dead. Her job is to hunt the ghosts that still linger, a dangerous and lonely position where she every year is made to fight others to not be replaced. When she meets the ghost of a super soldier, Wasp strikes a deal with him to help him find a long lost friend in exchange for learning more about the world that once was.

The Spider and her Demons by sydney khoo*

Young adult fantasy. All teenager Zhi wants is a normal life (and possibly for her harsh aunt to be a bit nicer), but it’s hard when she’s half spider demon. Every day she must conceal her true nature and hide in human guise. When she slips up and eats a man in front of her rich, aloof classmate Dior, Zhi thinks her life is over. But Dior has secrets of her own, and she is dead set on making herself part of Zhi’s life.

Not canonically aro and/or ace but have The Vibes

Lycanthropy and Other Chronic Illnesses by Kristen O'Neal*

Priya had plans to go to Stanford, but is derailed by the fallout of lyme disease, making her question if she’ll ever get back to normal. Luckily she has her discord support group with whom she can chat and vent about her illness. Even more - she has Brigid, online fandom friend and fellow chronic illness sufferer. But when Brigid disappears from the web without warning, Priya must drive to Pennsylvania to make sure her friend is okay - and finds that Brigid’s condition is a bit hairier than expected.

Project Hail Mary by Andy Weir*

Ryland Grace just woke up from a coma, unable to remember anything. He finds himself alone on a space ship, and as his memories slowly trickle back, he realizes he’s been sent on a mission: to find a solution to the impending doom of planet earth. Still struggling with holes in his memories, Ryland tries to fulfill his mission, but as he gets closer to his goal, he discovers someone else got there first. And they aren’t anything close to human. Funny, heartfelt, and heavy on the science.

Malevolent by Harlan Guthrie*

Lovecraftian horror mystery. Private detective Arthur Lester wakes up in his office, his partner dead, memories fuzzy, vision gone, and the voice of a malevolent entity in his mind. Unable to see, Arthur is forced to rely on guidance from the entity as they attempt to solve the mystery of what it is and where it came from. Is this a book? No. But as someone who reads mostly audiobooks, the difference between a book and a fiction podcast is negligible, and also I love this story and its characters and want all of you to do so too.

The Girl from the Well by Rin Chupeco

Young adult horror. Okiku died three hundred years ago, her body thrown down a well. Now she spends her days hunting for and punishing murderers like the one who once killed her. When a strange boy bearing odd tattoos appears in her area, he catches Okiku’s attention - as does something that follows after him. To save the boy, Okiku will be drawn into a journey taking both of them from American suburbia to a faraway shrine in Japan.

Radiant by Karina Sumner-Smith*

In a world where magic is currency, Xhea, wholly devoid of magic, is the lowest of the low. She does have one special ability, though: she can see ghosts. This ability proves useful when she meets Shai, the ghost of a girl from the higher echelons of society who isn't actually dead yet. Her body stolen and her ghost on the run, Shai needs Xhea's help.

A Closed and Common Orbit by Becky Chambers*

Technically part two of a series, but stands well on its own as the installments are only loosely connected (though I recommend reading the first book as well, it’s very good). A former ship’s AI recently moved into an illegal android body tries to make sense of life as she navigates her way through humans and aliens alike, paralleled with the story of a young girl working alongside and AI to flee a dystopian planet.

A Psalm for the Wild-Built by Becky Chambers

Novella. Long ago, robots, upon gaining sentience, simply laid down their work and walked into the wilderness. Long after, a tea monk looking for purpose follows after them into the wilds, where they come across one of the robots seeking its own sort of answers. While not plotless, this story focuses more on character and vibes over plot. Also has a nonbinary main character and features conversations on gender between human and robot.

Zero Sum Game by S.L. Huang*

Cas Russel is more than just good at math - she can calculate accurately and quickly enough to dodge bullets and fight those twice her size with ease. She thought she was the only one with an ability like this, until she discovers someone with a power even more dangerous than hers, able to reach into and twist the minds of others. Suddenly too involved to simply run away, Cas must not only save the day, but do so while she can't trust her own thoughts.

Skulduggery Pleasant by Derek Landy*

Young adult. Twelve-year-old Stephanie Edgley’s uncle, famed horror writer, just died mysteriously and left her his entire fortune. As it turns out, the stories he wrote weren’t entirely made up, and that which killed him wasn’t entirely human. In trying to avenge his death, Stephanie joins forces with Skulduggery Pleasant, sorcerer, detective, and living, walking skeleton. Including this one is kinda cheating because (part of) the series has romance, but the central relationship is always the codependent nonsense (affectionate) between the lead and her mentor/detective partner.

When the Angels Left the Old Country by Sacha Lamb*

The angel Uriel and the demon Little Ash have been friends for centuries, living and studying together in a small Jewish community in Europe. But times are changing, and many of the community have left for a new life across the sea. When one of these emigrants go missing, Uriel and Little Ash decide to leave their peaceful life to go find and, if needed, save her.

Ancillary Justice by Ann Leckie

A space opera in which sentient spaceships can walk the ground in stolen human bodies, so called ancillaries. One of these ancillaries, the sole survivor after the complete destruction of her ship and crew, is one the hunt for revenge against the most powerful woman in the empire. This series also does very cool things with gender!

Translation State by Ann Leckie*