Six Wakes, Mur Lafferty. I'm a huge sucker for this kind of thing - six clones wake up on a spaceship in deep space, their previous iterations murdered, what happened. The combination of the train/island murder mystery and the amnesia hook, And Then There Were None, They Were Eleven (which I hardly remember now, except that I was into the premise), the first season of Lost where they figure out that someone wasn't on the plane - and a couple of y'all may recall that I once ran a one-shot along similar lines. :) It's hard to say much else without undercutting the suspense, when part of the suspense, I think, is "is this well-constructed, is it going to be satisfying". So I will just say that it reminds me a lot of what it seemed like Lost wanted to be, with backstory character-revealing flashbacks and a foreground mystery, but is a nice standalone book instead of six seasons of inconclusive ad hoc bullshit, how about that?