Dumbledore isn't fooled though - and quickly picks out his old friend Horace Slughorn. He finally, with the help of Harry, convinces Horace to come back to Hogwarts and teach. Security has been increased around Harry every since the ministry acknowledges the return of Voldemort. While at the Burrow, Harry runs into an old friend Fluer who, he finds out, is engaged to Bill - much to Mrs. Weasley's displeasure.
When everyone arrives back to Hogwarts, things appear to be the same. During their first night back though, they learn that Snape has finally gotten his dream job - teaching the Defense Against Dark Arts post while Professor Slughorn will be the new potions teacher. Harry, who thought he wouldn't be able to take potions borrows an old potions book that was once owned by a person going by the name of Half-Blood Prince. The book owned by the Half-Blood Prince has markings that help Harry with potions and soon Professor Slughorn believes that Harry is a pro at potions.
Harry though begins to suspect that Draco is a new Death Eater, and that Professor Snape is helping him. No one will listen to his crazy ideas, especially since Dumbledore believes Snape to be on the side of the Order of the Phoenix. Dumbledore has also started to teach Harry on his own about Voldemort's past. But Harry can't let the feeling go that Draco and Snape are not up to any good. Will Harry be able to change Dumbledore's mind?
I think I liked this book even less than the previous five. For one thing, I didn't like how Harry (SPOILER) became quickly infatuated with Ginny - it was literally over night. His every thought was of her or Draco. It got a bit irritating to read "and the monster reared it's head in the delightful news and began to purr with happiness" or whatever feeling it was experiencing. It was like a splash of cold water on the face - abrupt and unpleasant.
Furthermore, what is it with her and (spoiler) killing off the characters? Dumbledore - Really? I'm trying to think about it from her point of view, as a writer trying to make the plot more interesting. It still would have been interesting but oh well. I vaguely remember the 7th book and the part I do remember I did not like. Harry still irritated me a bit in this book, although not as much as the previous book.