Harry Potter and the Half Blood Prince     

The sixth book in the Harry Potter series and the penultimate book before The Deathly Hallows. 

Here's the plot:  after the last year ended Harry has become a glum Gary after seeing his godfather Sirius Black die right in front of him.  Dumbledore has a cursed black hand after wearing the gaunt ring one of  ‘he who shall not be named’s’ horcruxes- a horcrux is a object fitted with the person’s soul.  Anyway, dumbledore and his cursed hand go to an abandoned house to find a guy named Slughorn who has been hiding from Voldemort’s deadly servants, aka the death eaters.

Here's a list of things that happened at or not at Hogwarts:

1:  Narcissa Malfoy and Bellatrix Lestrange convince Snape to make an unbreakable vow  (an unbreakable vow is a vow you can't break if you break it you die)  to protect Draco Malfoy.

2:  Slughorn replaces Snape as the potions teacher,  Snape becomes the Defence against the dark arts teacher.

3: Harry and Ron get new potion textbooks, apparently Harry’s one belonged to a guy named the Half Blood Prince (SPOILER - later it’s revealed the Half Blood Prince is Snape)

4: Harry becomes top of the class in potions and gets a vial of the luck potion Felix Felicis, also known as liquid luck. 

5: Harry joins the slug club,  a  group of Slughorn’s most talented well-connected students. Ginny and Hermione are also part of the club making Ron feel left out.

6: Harry starts to slowly develop a crush on Ginny 

7: Harry and Dumbledore go into a remote cave to find a third horcrux, the locket of Hogwarts founder Salazar Slytherin (it’s revealed the horcrux they found was a fake) 

8: Snape kills Dumbledore, and he falls off the Astronomy balcony.   Snape did it because he was being a double agent for Dumbledore.  

9: The death eaters take over Hogwarts leaving the sixth book on a cliffhanger. 

I rate Harry potter and the Half Blood prince- 5 Dumbledore betrayals out of 5 Felix Felicis vials. 

Now it's time for the Final Battle,  the battle of good and evil, the Final book-   Harry Potter and the Deathly Hallows!