In the penultimate installment to the Harry Potter Series, Harry comes much closer to killing Voldemort than before. Snape shows his true colours, - Snape who Harry finds out is the Half-Blood Prince - and Malfoy is given a difficult task. This book is action packed, and nearly got me crying when Dumbledore dies. As a reader you wonder what more can be taken from Harry by the Dark Lord. Definitely one of those books that keeps you in suspense as Harry inches closer to destroying Voldemort.
Harry and Dumbledore set out to destroy the Horcruxes that have helped Voldemort to become immortal. Harry learns a great deal about Voldemort through memories that he and Dumbledore examine in Dumbledore's pensieve. Harry sees that he and Voldemort are not that different in the circumstances of their lives.