Snape is the one continuing element of these books that I always severely question. Why would you, as an author, present people with such a dangerous person as a teacher without even asking any questions about it? Like, that could be a minor theme, and Rowling never really engages with it because she doesn't seem to know how she wants to view teachers as people.
It's one thing to hold grudges against people (Sirius Black and Remus Lupin, in this instance) for things they've done to you, but it's an entire other thing when your teenage grudge continues to plague your life and your profession (and, as a result, the relationship that you should be building with your students). This is something that I can, from experience, discuss. In the international school circuit, you often work with the children of your colleagues (and while it's preferable that you like them, it sometimes happens that you don't). If I let my feelings for my students' parents cloud my judgement, I would be treating so many kids badly. I'd hope that my boss would talk to me about this and set me straight (or straight up fire me for too many transgressions, let alone outright abuse).
The child of a person (or the godchild of a person) is not guilty of the crimes of the parent or guardian. The fact that a grown man is taking out his teenage feelings on the child of someone who he felt betrayed by is beyond disgusting. And it still leads right back to my constant question: What is happening in Hogwarts' management that they enable this behaviour? And why does Rowling never make this a question that is asked or considered?
It just perpetually frustrates me that no one seems to be actually managing the school and ensuring that it is a safe place to be, even in the background. Maybe it's just Minerva on her own, yelling at everyone to fix shit because they're all too busy holding grudges or acting mysterious while being overly-well-informed but doing little else than spouting cryptic messages.
That said, the events of this book are a bit more interesting, though I'm still of the opinion that Quidditch scenes are beyond boring and provide further evidence that they care little about student welfare and are in desperate need of a child welfare check. The fact that Harry can't go to Hogsmeade because his abusive aunt and uncle didn't sign the permission form but can play in a Quidditch match (especially during a massive rainstorm with a near-tornado) is ridiculous. They're fine with him flying around on a broomstick with little protection and a potential for extreme injury, but he can't just go hang out in town at a tavern. Again, no questions asked about this kind of logic.
The introduction of Lupin, Sirius, and the Marauder's Map is one of the better aspects of this book. Having Lupin excitedly describe how Sirius, James, and Peter just casually broke the law in order to become Animagus and keep him company during his turns is quite nice. Though, as for Peter, while this book fleshes out that part quite nicely for his existence as Scabbers, it's disappointing in review of the previous two because there was so little done to even hint at that other than to say he was "passed down" and missing a toe, so it feels like it wasn't originally mapped out nearly as well... Sort of like it was more an accident that Scabbers could be something more important.