In an attempt to get Half-Blood Prince done before Book 7 comes out  I'm going to try to go quicker with the chapter summaries and to emphasize the high-points in order to get more chapters out more quickly. So without further ado...
Chapter Eight: Snape Victorious
When we left Harry he was under a spell, under his Invisibility Cloak hidden on the Hogwarts Express. Tonks finds Harry and fixes his nose, though Harry is somewhat nervous about it. They jump from the Express as it is already leaving, and watch it until it is out of sight. Tonks sends a Patronus up to the school to let them know that Harry is safe, thus confirming that the Order can use a Patronus as a means of communication.
Harry asks what Tonks was doing here, and she replies that she is stationed in Hogsmeade along with 3 other people. When they get to the gates, they are chained shut. Harry tries "Alohamora", but Tonks says that won't work because Dumbledore bewitched the gates himself. Harry says that he could just climb the wall, but Tonks again says that security has been "tightened a hundredfold" since the summer. Here we have the security of the School emphasized once again, foreshadowing the ideas that either someone will try to break into Hogwarts or someone will indeed succeed in breaking into Hogwarts.
Who should show up to pick Harry up but none other than Severus Snape. Snape is his usual self, throwing around insults. Tonks apologetically says to Harry that she meant Hagrid to get the Patronus, but Snape says that Hagrid was late to the start of term feast. Wonder what Hagrid is doing?
Snape also tells us that Tonks Patronus has changed, and he thinks it looks "weak". This is fascinating to me. What can make a Patronus change? Would having someone close to you die cause it to change? Or perhaps any strong emotional change could cause the Patronus to change shape. And why does Snape think it looks weak? Is it simply because of its shape?
Harry's "hatred" for Snape is re-emphasized during the walk up to Hogwarts. Snape takes points away from Gryffindor and embarrasses Harry by making him walk into the Great Hall without his Invisibility Cloak.
Ron mentions that the Sorting Hat once again was "advising us all to unite in the face of our enemies..."
Harry fills Ron and Hermione in on what Slughorn wanted at the Party. Hermione also notices Dumbledore's blackened hand. Harry expresses wonder at the fact that neither he nor Madam Pomfrey have cured it yet.
Dumbledore announces that any items from Weasleys' Wizard Wheezes are banned. 
Then the bomb drops. Dumbledore announces that Slughorn will be the new Potions teacher. Potions teacher? Well, who will teach Defense Against The Dark Arts, then? None other than Professor Snape. But why would Dumbledore make Snape the DADA teacher? Harry thinks to himself "Hadn't it been widely known for years that Dumbledore did not trust him to do it?" Have we been taking this mistrust for granted, though? And if the mistrust really was there, what made it change?
Some would say this decision is so out of character that it should be added to the list of evidence that Dumbledore is not himself. Others would say something must have happened to make Dumbledore trust Snape.
Once we get further in the book, I want to talk about the parallels between this event and another certain Someone who also wanted to teach at Hogwarts but who Dumbledore never gave permission.
Harry points out that at least Snape will be gone by the end of the year as no DADA teacher has lasted longer than a year because "That job's jinxed...Personally, I'm going to keep my fingers crossed for another death..." Unfortunately, that death may not be who Harry wishes...
Once again Dumbledore emphasizes that it is dangerous and that the school's security has been hightened, again possibly foreshadowing that even though security has hightened, someone will break in.
After Hagrid explains that the reason he was late was that he was with Grawp, the students leave for their dorms. | 
