Although I have marked it a 3 it is more a 3.5 star for me. I love the mystery in Agatha Christie novels and this one did not disappoint either. From the beginning I was trying to guess who the murderer was (like always) but no luck this time either. The suspense was really good through out the book but the final reveal felt lacking. I found And Then There Were None much better. 
 (view spoiler)[ As the book is written from Dr. Sheppard's point of view I think it is but natural that you don't realize he is the killer. This sort of took the whole fun out of the book at the end for me. I found the smaller mysteries much more entertaining and was able to guess a couple of them. (hide spoiler)]