Harry Potter and the Half-Blood Prince by J. K Rowling

In the sixth installment of the series, the protagonist returns for his sixth year at a magical school, where he excels in potions class with the help of an old textbook once belonging to the mysterious "Half-Blood Prince". As he delves deeper into his enemy's past through private lessons with the headmaster, he learns more about the Dark wizard's history and his own destiny. Amidst this, the school is no longer the safe haven it once was, and danger lurks within the castle walls. The year ends with a devastating loss, setting the stage for the final showdown.

The 628th greatest book of all time