I bought this because the premise sounded like a lot like that of the movie "50 First Dates"... or rather, as if "Before I Go To Sleep" starts where "50 First Dates" ends. It very quickly became obvious that that wasn't the case, and that this book was a lot more sinister and slowly turned more and more terrifying.Very well written, and I had a very hard time putting it down, but unfortunately the end left me oddly unsatisfied. As usual (grrr!) the bad guy got off too easily (why is that so often the case?!) and I would have loved just one more chapter to get everything properly wrapped up.But since I enjoyed everything up until then, I'm still going to give this 4 stars.