The Twilight Saga, Book 4: Breaking Dawn 

When you loved the one who was killing you, it left you no options. How could you run, how could you fight, when doing so would hurt that beloved one? If your life was all you had to give, how could you not give it? If it was someone you truly loved? To be irrevocably in love with a vampire is both fantasy and nightmare woven into a dangerously heightened reality for Bella Swan. Pulled in one direction by her intense passion for Edward Cullen, and in another by her profound connection to werewolf Jacob Black, a tumultuous year of temptation, loss, and strife have led her to the ultimate turning point. The astonishing, breathlessly anticipated conclusion to the Twilight Saga, Breaking Dawn illuminates the secrets and mysteries of this spellbinding romantic epic that has entranced millions.