Short List by L.R. MacAllister

Having less than six months to live, a terminally ill writer embarks on a coast to coast road trip. Seven names are on his list: the ones who had stolen from him in various ways and would pay the ultimate price for their transgressions. His latest manuscript, about a serial killer, had been rejected by every literary agent he'd send it to, but its research has not been in vain. Less than 50% of homicides are solved. The odds are in his favor.