It is always fun when reading a novel to have either been to the place where the story is set or know the area well.  Patrick Oster of Westchester is the author of a new novel, “The Commuter,” which deals with a laid off office worker who spends his time tracking the “clandestine and criminal activities” of his fellow Metro-North train riders.  Oster is himself rides the 6:19 a.m. train from Croton-Harmon to Grand Central every morning.  He got the idea for his novel from observing his fellow commuters each day.  He said in an interview in Tuesday’s, August 5, Journal News that he always wanted to create a character that would do what he always wondered about–follow people on a train.  Oster said he wrote a great deal of the novel on his laptop while commuting to and from his home on Metro- North