Vee's diagnosed as narcoleptic. When she tries to tell her father what's really going on, he thinks she's upset because of her mother's death and sends her to therapy. Needless to say, she's wary about telling anyone else, including her best friend Rollins. When she sees a person writing a suicide note, standing over the body of her sister's best friend, Vee knows she has to do something. She just doesn't know what. Or who to trust. 
 This is a true high-school book. Too-absent parents. Lots of high-school garbage to deal with: rumours, back-biting, sex (not graphic, but does include an interrupted date-rape scene), cliques, drinking, cheerleaders, lies. I think most readers will figure out who-dun-it fairly easily. The clues are all there, though Hathaway does give us some credible red-herrings. 
 Ultimately about Vee figuring out some things about herself, her friendships, and her family.