Just finished reading it (I got it out of the library after seeing your recommendation here).
I confess I did not see the ending until it occurred (see below folks unless you haven't read it yet). But once I got used to the flashbacks and different narrative voices, then yes I agree it was a terrific read. But I couldn't really warm to any of the characters, an odd bunch and quite nasty.
SPOILER Below:
Do you mean you foresaw Anna helping to murder him, because I didn't and that final twist (pun unintended) was the icing on the cake for me.
I did however have a strong inkling some time before the end about who murdered Megan.