The last book in the Harry Potter series is "Harry Potter and the Deathly Hallows." Published in 2007, this seventh installment concludes the beloved saga created by J.K. Rowling. The story follows Harry Potter as he embarks on a quest to find and destroy Voldemort's Horcruxes, integral to defeating the dark wizard. Themes of friendship, sacrifice, and love are central to the narrative, culminating in a climactic battle at Hogwarts. "Harry Potter and the Deathly Hallows" ties up numerous plot lines established throughout the series and has been praised for its emotional depth and mature storytelling.