Slow to start, but really, really good when it finally reaches the end of the first part. Alternating the points of views was a great idea, and it's well executed. 
 (view spoiler)[I completely fell for the twist. There I was, flattering myself that I had guessed everything, that's Nick's penchant for the "lies of omission" meant that he had omitted to tell us of his murdering his wife... and then blam, the 2nd part hits. That was really, really well done. 
 However, I wish the author hadn't swapped one cliche for another, the naive victim, however likeable, for the femme fatale, the cunning mastermind. Amy is still flawed, and she's a great character, but I was hoping for a second twist, to be honest : after all, we had been tricked once, couldn't we have been tricked twice ? (hide spoiler)] 
 I'm looking forward to see how it translates into film, especially now that I know that Gillian Flynn wrote the script herself (or participated in it). 
 I had great fun, found myself completely hooked, even though I wasn't happy with a thing or two, in the end it completely deserves its fame.