Breaking Dawn (Twilight, #4) by Stephenie Meyer
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, she has endured a tumultuous year of temptation, loss, and strife to reach the ultimate turning point. Her imminent choice to either join the dark but seductive world of immortals or to pursue a fully human life has become the thread from which the fates of two tribes hangs.
Now that Bella has made her decision, a startling chain of unprecedented events is about to unfold with potentially devastating and unfathomable, consequences. Just when the frayed strands of Bella's life - first discovered in Twilight, then scattered and torn in New Moon and Eclipse - seem ready to heal and knit together, could they be destroyed... forever?