Hard for me to rate this book. It is so... weird? Anti-conformist, in its themes and the way it treats these? While one of the main subject is conformism itself, making the book... my head hurt. What I mean is, this story is well written. I felt the convenience store, understood the points of the author, and somehow the character grew on me. 
One thing though; that woman exhibits all classical signs of a psychopath. Does she NOT become a serial killer only because she's being conditionned into being a "convience store woman", as she put it? This never get resolved, and I'm left wondering if there's something I missed or did not get.  
Also, the way society works in Japan is very different from the west. Which isn't a surprise, but still, I do find it harder to relate. In Europe, while you can very well get judged for not being married or not having "a career", it'll be more discreet, more in-your-back than what I just discovered. The dialogs felt very much foreign a lot of the time, and they are, but it didn't help the case of a book that's already particular, therefore not everyone's taste. 
Still, a story to be read, to take a long look at capitalism and society's expectations of its people.