Before I Go to Sleep

First novel. An Amazon recommendation for June 2011. Total amnesia combined with inability to form new memories are the plot devices. The main character wakes up every day wondering where she is and what is going on. By the end of the day she realizes that everything that she's experienced that day will be forgotten in the morning. Who should she trust and why? Been covered multiple times but that doesn't mean this one isn't good. Very well done. Very enjoyable.