Book Project Thing
The book is Mr. Mercedes By: Stephen King
Plot...I've had to rewrite this a billion times because my computer is being stupid.
So, in the book, the main character, his name is Bill Hodges and he's a retired detective, so he's depressed or something. But he gets a letter from the guy who killed all those people at the city center. So Hodges gets all excited and he tries to figure out the mystery by himself (even though he's retired). So we also get some of the story told from the killer's point of view (his name is Brady Hartfield). Anyway, so, yeah, Hodges goes most of the book trying to figure out who the killer was so they can get the dude behind bars.