What is the resolution of Harry Potter and the Half-Blood Prince?

In "Harry Potter and the Half-Blood Prince," the resolution centers on the devastating loss of Dumbledore, who is killed by Severus Snape, revealing Snape's complicated allegiance. Harry resolves to seek out and destroy Voldemort's Horcruxes, understanding the gravity of the fight that lies ahead. The story ends on a somber note, emphasizing the looming battle against dark forces while highlighting themes of sacrifice and loyalty among friends.