Legion by Brandon Sanderson

"Stephen Leeds, AKA 'Legion,' is a man whose unique mental condition allows him to generate a multitude of personae: hallucinatory entities with a wide variety of personal characteristics and a vast array of highly specialized skills. As the story begins, Leeds and his 'aspects' are drawn into the search for the missing Balubal Razon, inventor of a camera whose astonishing properties could alter our understanding of human history and change the very structure of society"--From publisher description.