I wonder for how many people, the book works because they don’t know much about these characters otherwise. I imagine that Patroclus was more interesting, as anyone with a name in Iliad usually is, but other than a reading of the odyssey and some other I can’t remember, I’m not well versed in the Iliad. So I get a blank slate to start with, and can take these characters as kind of a fan fiction almost, honestly. I’ve referred as “a retelling” in some other comments, but I didn’t read it with that idea in my head. I assumed it would be far different from The Iliad, and I think the disconnect, and ignoring some other things (I also thought Patroclus was a flat—he gets more interesting in the end when he starts to become his own person and interact with people and gets out of Achilles shadow—and has a conflict with and major contrast to Achilles), is the reason I still enjoyed it. Sometimes I just want a good story and I’ll ignore everything else, to be honest, so I can understand the reasons to dislike it, I think.