I'm not normally a fan of anything that might come under the heading of "thriller", but my god, was this book good. 
 I'd already been a bit spoiled for some of the plotlines - though there was still enough in there to keep me guessing - and the use of the unreliable narrator (always a favourite technique) meant I was completely stumped over certain things. 
 I'm really interested to see how the book has translated into film - I'm planning to see it in the next few days, and it'll be interesting to see how they've made it work, especially some of Amy's early chapters. 
 Spoilery thoughts below. 
 (view spoiler)[ So all I'd been really spoiled for was that Amy was something of a sociopath, and that Nick didn't kill her. And despite knowing this, I found it really difficult to hate Amy or like Nick - maybe Amy's that good, that the "diary" works through the page too? Or maybe I should just be worried that I could sympathise with her. I guess I just buy into the Ellen Abbott school of thought - it's always the husband's fault, because that's the way it is in all the tv shows. Regardless, I loved the ending - nothing sickly sweet, no comeuppance, just closure, of a sort. (hide spoiler)]