I liked the development of the characters. Lou, in particular, felt very real. I empathized with her a lot and hated how her family treated her. I didn't like the changes in POV in the book and didn't feel that they added to the story. 
 (view spoiler)[As for the ending, I was not a fan of Will's decision. Even if he had struggled with it and made up his mind in the two years prior to the book chronology, this should have been discussed or explained more. What ended up was a very dispassionate feeling to a very intense decision. And I'm sure the author didn't mean to have it sound flip. The whole scene in Switzerland needed to be expanded more, in my opinion. (hide spoiler)] 
 Overall, I found it an absorbing read, especially in the second half. It's not necessarily a book that I would read over and over, but I'm glad that I have read it and am working my way through the sequel.