Th Invisible Ones by Stef Penney

This mystery, if there is any truth in it, is a window into 1980's Romany culture in England.  Private investigator Ray Lowell is hired to find a young woman who has disappeared following her marriage to a young Romany man, Ivo Janko.  Lowell tells the story from two perspectives - from the beginning of his investigation and from from his current position in a hospital bed with a mysterious illness that has clouded his memory.  The third voice telling the story is a young Romany boy, JJ, a relative of Ivo's.  There are many twists to the plot which predict a strange resolution but I'm guessing you won't guess this one.