It is interesting how authors handle protagonists who aren't human, especially when the author does it well. Of course, not any technically not human protagonist really counts. Lots science fiction or fantasy have protagonists with protagonists that are technically not human, but really are just humans with a twist. That elf might technically not be human, but really, it’s just a long-lived human from a culture with a preference for bows.
What I am talking about is when the author leans into this difference, when not being human is part of the point. A great example is the Books of the Raksura series by Martha Wells, where the protagonist in the main is a Raksura, a vaguely human species with wings that live in ant-like colonies with queens, workers and warriors. It’s even not quite one species but a couple of species in a sort of symbiotic relationship. The ecological, cultural and biological implications of this species’ nature and their colonies are an essential part of the books.
Importantly, Martha Wells doesn't go too far in the alieness of the Raksura, because that would get in the way of being able to connect with the characters as a reader. In some ways things still play out with very storytelling formulas. The queen of the colony still needs to mate, so Martha Wells throws in a good helping of romance tropes, just with some really refreshing twists. In other ways it plays out like a traditional fantasy adventures, with a fellowship heading out on a quest. The world also has human in it to provide contrast to Raksura.
The book that got me thinking about this topic is The Raven Tower by Ann Leckie. Who the protagonist is in this book is, is tricky because of the way the narrative is constructed. The book is told in first person from the point of view of a god, who is also a stone. Leckie does amazing job communicating the stones perspective, getting across the age and patience of the stone. At the same time the book is also in second person because the plot is told by the stone to a human as the human is going through the main plot. In between the second person section the stone reminisce about past events that brought about the current situation in first person. This setup does make the book harder to read, and it speaks to Ann Leckie's skill as an author that she can make it flow so well. Another thing that helps underline the difference between the god and humans is that the stone god and the human have different goals and desires but both are explained by the god. How the god thinks about things and how the god thinks humans think about things.
The Raven Tower is a great book but it’s not as good as Ann Leckie's other series with a non-human protagonist Imperial Radch. Here the protagonist is an AI. A bit of a science fiction staple, sure, but done here with impeccable skill. This is not some boring, cold, logical AI. It has a rich inner life and a philosophical approach to life. This series has won a lot of awards, all of them deserved.
The best books with an AI protagonist are not Imperial Radch. That honor has to go to The Murderbot Diaries by Martha Wells. This AI is a SecUnit, a sort of android that provides security in scientific expeditions and the like. This one though, has hacked its own governor, giving it freedom to ignore commands and pretty much do what it wants. The typical trope of AIs in science fiction is that they are emotionless and pure logical. Martha Wells goes in the complete opposite direction. With a complex enough AI you want it to have a rich set of fears and desires to guide its actions. So, in this world the really complex AIs like the SecUnits are a lot more emotional than humans. The end result is not just a very engaging protagonist, but maybe the most sympathetic one I've ever come across. The series is about the SecUnit trying to make sense of its own nature and place in the world all the while trying to hide the fact that it is a rogue AI. Beyond the advantage of a great protagonist the Murderbot Diaries also has amazing writing that is witty and charming, and flows so very easily. It’s the kind of writing where by the time you've finished the first paragraph you are hooked and won't be able do anything else until you've finished all the novellas. I recommend the series very highly.