
Reading it for a third time however did make me realize that this book has quite a few criticisms of the British Class system and could only have been written by someone from the Working Class. Maybe I'm only thinking this because I know Rowling's background but let us look at the evidence.
In this volume we really get a better picture of both the Weasley and Malfoy families. The Weasleys are obviously supposed to be loved by the reader. The dad has a difficult middle management job that he works at to support his family, the mom works all day to keep the household running and each of the many kids are lovable in their own way. They don't have a lot of money and the younger kids get everything second-hand. You never feel bad for them, they do have enough, but just barely and it requires constant work. Very middle class and throughout the series the Weaselys are at the very heart of the story. Compare this to the upper class Malfoys. The dad, Lucius, is on the board of governors at Hogwarts, is able to pull political strings to get Dumbledore removed, and hates people that are either somewhat poor like the Weasleys or have Muggle parents. He seems very concerned about peoples' heritage and wants to make that a condition for magic education. His son, Draco, basically copies his dad's opinions and believes that he's superior to everyone else at the school based on the family he comes from.
Then throughout the story there is much discussion about who is the "Heir to Slytherin". Draco wishes that it was him, while on the other hand Harry hopes that he isn't the heir. Basically both see that position as being a form of royalty and Draco wants it and Harry rejects it. Harry is afraid of this power that is handed down from previous generations while the entire Malfoy family pledges their allegiance to whoever holds this power. So basically Rowling shows that the working class is good, the upper class is bad, and power shouldn't be handed down based on any type of birthright.
Also there is the whole case of Gilderoy Lockhart. The book doesn't say too much about his background, but within the wizarding world he is considered a celebrity and appears to be wealthy. By the end of the story we find out that he is a total fraud and is only concerned with appearances and is actually not very nice at all. Another strike against the upper class.
Then there is Harry Potter himself. He may technically be very wealthy, but he has a very middle class mindset since he was raised by the Dursleys. He feels bad when he sees the Weasleys struggle and wants to help them but doesn't know how to without hurting their pride. Also when he sees that the Slytherin Quidditch team has far superior brooms than the Gryffindor team, it doesn't even occur to him that he could use his own money to level the playing field. Using his fortune to help himself isn't how Harry solves his problems.
Oh yeah, I almost forgot about Dobby! He's basically a slave for the Malfoys. And at the very end Harry frees Dobby from the Malfoys and Lucius is mad that he's lost an elf slave.
So I wonder if all of this was intended by J.K. Rowling to get a point across or just shows her personal feelings and background.