The Beautiful Dead: Jonas by Eden Maguire

Something strange has been happening at Ellerton High. Four teenagers dead in a year, all dying in freak and sudden circumstances. Darina's boyfriend Phoenix is the fourth to die and she longs to see him again. When he appears to her and during the time that they are reunited he tells her about the Beautiful Dead. Darina then gets a mission: to help the four dead teenagers find out the causes of how they died.