My review will be similar to some others I'm afraid. A real mixed read for me. I like alternating chapters, giving the story from different views and that worked well here, although it did (intentionally?) give away a major plot element early on, and left me feeling quite uneasy about the whole story going forward. Strangely, I read all the characters as much older than they turned out to be so had to rethink that slightly.
Mary's story was compelling and believable. Murray made sense. Julia was just plain irritating and honestly, a good read could have been made just out of Mary's story and seeing that through to the end, without Julia even being there (with tweaking obviously - says me, who has never written anything in my life!). The twist at the end was good and I didn't see the ultimate reveal coming until very close to the end.
Not a bad read at all, and I can be a bit impatient with flakey or overly emotional characters sometimes, so that may account for my irritation with Julia. Worth a read just for Mary's story.