Well written & mesmerizing. I Loved this and can't wait to read more from Daphne du Maurier. 
 I read this as part of a group read in my classics group about a month ahead of the group so as to be able to see the movie when it came out in June. I felt like I figured it out for certain, about half way through and never changed my opinion after that. Despite having "figured it out", I was still captivated with the suspense of finding out how and when the characters would find out and what would become of the realization. I never understand when someone doesn't like a book because they "figured it out". It's not always about you, it's about the characters! Did you figure out how each character would figure it out and when? Did you figure out how each character would respond? Those are the real questions when it comes to good mystery. I find it more annoying when a book makes it practically impossible to figure it out, just so all readers are surprised. 
 I was prepared for our group discussion to have many not like this book for the "figured it out" reason. Boy was I wrong! As it turns out, I'm one of the few (maybe the only one) who feels certain. Most people in the group found the ending to be ambiguous, and most leaned towards my opposite conclusion! This made me love the book all the more. Yes Philip is a spoiled immature brat who drives you crazy. He is supposed to! I wanted to strangle him many times and that added to my enjoyment. 
 The film made the conclusion much more ambiguous and my friend expressed frustration about it afterwords. I told her that the book was more definitive, because of this that and the other facts that were left out of the film and this other fact that was added. She said, "oh, I like that much better" . Now I have to tell her that many others still found it ambiguous, so she just needs to read the book. I loved the film too by the way. I rarely have problem with a film not following the book exactly. I usually enjoy differing interpretations. That's part of the enjoyment of art and why it's so much better than politics.