The Ghost Writer by Alessandra Torre

Helena Ross is a famous writer of successful romance novels and she is dying.  With just months to live she has one more book she needs to write and it is to be her confession.  Readers of her novels could not have imagined her life of isolation.  When she realizes that she is not well enough to finish the book, she decides to hire a ghost writer.  Surprisingly, her choice is Marka Vantly, her major writing competitor.  But Marka is not who Helena imagines.  There are secrets everywhere that make the book hard to put down.  The clues to the "confession" are slowly released mixed in with back story of a life that is unravelling.  This is easily a one sitting read.