This is the third book in the Twilight series call Eclipse.
Edward and Bella are back together, permanently this time. She's going to become a vampire after her high school graduation and she wants Edward to be the one to do the job. His only condition for this is that she marries him.
In the meantime, Seattle is being ravaged by a "serial killer" that is really an army of newborn vampires that are unable to control their bloodthirsty urges. These newborns are being created by Victoria, who has wanted Bella dead ever since the end of Twilight. It is up to vampire Edward and werewolf Jacob to unite the good vampires and werewolves in order to save Bella's life.
Bella learns that her heart is torn between her true love, Edward, and her unrequited love for Jacob. She realizes how her desire to become a vampire will impact the people she loves. She's torn between the mortal life that she loves and an eternity with her true love.
This by far in the best book so far on the series. I was very impressed the story line. It is pact with action and more romance. This is another book that I had a hard time of putting down. It made me very sad when I had finished reading the book. I have since read it two times and I am about to read for it for a third.