I know a lot of people disliked this book, especially compared with TTW. But considering it on its own, I quite liked it. 
 I mean, there are points that I didn't like about her book, like how the first part was extremely slow and the plot only picked up in the second half and how I think Elspeth's (the twin who is Robert's lover) characterisation could be better. Her thoughts and dialogue in the book seemed very trivial and didn't tell us much about her. (Actually, I found that there were lots of bits in the book that weren't necessary - it didn't help the plot or the characterisation. There were chapters I liked though - is this considered a spoiler? - like why Julia and Valentina remained virgins. It told me a lot about their relationship. But I digress.) 
 I knew a lot more about J&V's relationship than E&E's. I knew so little about Elspeth that the twist at the end was very surprising. Twists can be surprising, but not because we know so little about a character's character (oh gosh) that we have a false impression of their character, and the twist completely places him/her outside our false impression. Twists should challenge the reader to review our impression of a character, but the action should still be within the boundaries of the person's character in a 'if you think about it' way. I knew so little of Elspeth that when what she did surprise me, I was kind of 'why was I not told that Elspeth was this kind of person?' so it wasn't a really good twist. 
 There are people who can't accept that Elspeth and Robbert acceded to Valentine's request so easily. While I agree that that portion could be further developed so the decision doesn't seem so sudden/strange etc, I find that there are reasons presented for doing so. I.e. Elspeth being selfish, Robbert being such a pushover. 
 The big secret between Edie and Elspeth was so insignificant and pointless. Lots of people have ranted about this, so shan't go into too much detail. 
 I loved the ending though. It's not very predictable, and no one actually gets what he/she specifically wants earlier in the book (e.g. Valentina to be fashion designer and free from her sister), but sort of inadvertently gets what's 'best' for them (e.g. Valentina was happy and free of her sister). 
 I like Martin/Marijke a lot. Most people do. 
 I like her atmospheric writing, which is what most people like about her books. But some parts felt too simplistic though. Little annoying. 
 Oh, and someone also mentioned before that the rules of being a ghost weren't properly explained. If only being able to do certain things in a certain way had a rationale, it wouldn't seem like each rule was created to fit in with the story/allow the character to do a certain thing/etc. 
 Anyway, this review is incredibly disorganised. Oh well have fun reading. I procrastinated my homework quite a bit to finish the book and review here.