By Leslie Lindsay  Where does the truth lie and darkness begin? That is the question overarching this entire book, but there’s more: it’s about love, obsession, mental illness, jealousy, revenge, and so much more.  “We believe what we want to believe. We believe what we need to believe.” So begins EMMA IN THE NIGHT (Aug 8, St. Martin’s Press) and immediately, I was hooked. This is a voice-driven character and right away, I can tell she has a skewed version of the world. And what’s more intriguing than reading about an unreliable narrator? Three years ago on a foggy night, 15 and 17-year-old sisters, Cass and Emma Tanner disappeared from their home, seemingly walking into the shore of the beach ala Virginia Woolf. Everyone suspects they’re dead…and the investigation has come to a stand-still. And then, with just the clothes on her back, Cass returns home…without her sister. She talks of kidnapping and isolation, a mysterious island off the coast of Maine where the girls were held in a home by two strangers, a husband …