- HP and the Philosopher's (Sorceror's) Stone - that Stone is what the book's all about, finding it or taking it or keeping it safe.
- HP and the Chamber of Secrets - again, the book is all about the Chamber being opened and what happens then and who opened it.
- HP and the Prisoner of Azkaban - from very early on in the book, the existence of the escaped Sirius Black is what drives events, from the Dementors to the Grim to the dormitory breakin.
- HP and the Goblet of Fire - what's so significant about the Goblet? It appears for just a few short scenes IIRC. Why not HP and the Triwizard Tournament, or even HP and the Triwizard Cup if you want a physical object? Or even HP and the Yule Ball, aka Dating for Dummies: at least the Ball takes up a few chapters rather than just one or two scenes!
- HP and the Order of the Phoenix - again this is slightly odd, and surely HP and the Ministry Coverup would be a more relevant title. But still, this is the book that introduces us to the Order and its importance, and its members show up at all the key places in the story.
- HP and the Half-Blood Prince - I could think of more relevant titles, but Harry is learning a lot from the Prince throughout the book, and the revelation of his real identity connects up with the mega-event at the end of the book.
- HP and the Deathly Hallows - the learning curve is slow, but once we and the protagonists learn about the Hallows, it becomes clear that they're incredibly important and in a way the key to everything.
One title stands out among the seven for its apparent incongruousness and insignificance. Is there any record of why Rowling chose that title, or what other titles she considered?