Biggest weekness for me was the budding romance to be honest. It was quite uninteresting, and I don't even know why exactly.
The whole PI thing was set up well, the back story of her client as well, although the big conclusion was for me quite anticlimactic. It was against all odds, and actually it wasn't very original, it felt like a bad 90ies psycho thriller.
All in all it wasn't a bad read, but it didn't really feel motivated to pick up the next installment.