Godplayer — Robin Cook

In this “nerve-wracking” (Chicago Sun-Times) novel, a doctor discovers that neither her marriage nor her job is what she thought -- and her quest to find the truth may just kill her, from the #1 bestselling “master of the medical thriller” (The New York Times).
 
From the first moment pathology resident Cassandra Cassidy meets brilliant cardiac surgeon Thomas Kingsley, she knows they are meant to be together. Forced by a deteriorating eye condition to switch from her chosen field to psychiatry, Cassandra needs the support and approval the charismatic doctor so passionately offers. Thomas finds in the beautiful and vulnerable girl the boundless devotion he so desperately requires.
 
But as Thomas continues his meteoric rise, what should have been fairy-tale happiness begins to disintegrate. Saintly to an adoring public, Thomas is something other to the woman who loves him -- an erratic and hostile stranger whose inexplicable rages and bizarre behavior are increasingly disturbing.
 
As Cassandra's marriage begins to crumble, the dependable security of the hospital world around her seems equally menaced: Cassandra is convinced that someone is killing terminal patients -- someone who holds the power of life and death in his hands and wields it like the angel of death. When she takes it upon herself to stop the killings, she stumbles onto a terrifying discovery that opens the floodgates of unimaginable horror.