My Favourite book

I have read a lot of good books in my life, so I can't say what is my favourite. Since I was a child I like very much the books and the movies of Harry Potter, that is why I will talk about my favourite book of that serie. Its name is Harry Potter and the Half-Blood Prince, and it is the 6th book of the saga writed by J. K. Rowling and was published on 2005.
The book is about the 6th year of Harry Potter in Hogwarts, School of Witchcraft and Wizardry, the adventures and troubles that he had there, because his enemy (Voldemort) was reborn and is getting stronger, for this reason, Harry has to know his past to stop him, but it is difficult because there are others conflicts in the plot.
This book is my favourite because here we can know the secrets of the Voldemort's life, his past and how he ascended to power. Here we can see a lot of things that is not in the movies, and that is what I like the most, because when I was a child I loved the movies of Harry Potter, but I thought that the story was incomplete, so I decide to star reading the books in order to understand the story in a better way. 
I got all the books in different ways, however "The Half-Blood Prince" was a birthday present.