It was Charlie Holmberg's The Paper Magician, which is still one of my favorite indie fantasies for its sheer inventiveness. It was just a lot more so before the rewrite replaced some of that inventiveness with standard romance tropes.

Amazon also pushed updates to my ebook of Madeline Miller's The Song of Achilles that same year, but those were extras (albeit spoiler-containing ones) I was less irritated by it.