This book is told from the perspective of a middle class, American girl who is going through puberty. She tells her story in a funny, quirky way, always clearly maintaining her solidly middle class status throughout. She is not exclusive about it, just firmly centered there. There is HUGE number of product placements/ads that are infused throughout this entire series of books, and I find that annoying. That's why I gave it four stars.
Unlike some reviewers, I didn't find the discussion of menses and what the main character sees as the male equivalent (erections) to be offensive. Twelve year olds do have to deal with these issues, and this book addresses them with sensitivity.
So, if you can accept the flaws I've mentioned here then you may well find this to be a perfectly good piece of adolescent literature. I did.