This book discusses how girls can be the worst kind of bullies of all, employing microaggression and social freeze-out to punish those who displease them. It can often be so subtle and unspoken that even those being punished do not understand what's happening or sometimes even that it is happening at first.
The book discusses various forms this bullying can take, citing examples for real life victims of it. Later it discusses what parents and teachers play in all of this and what are the right - and wrong - steps to take when you're aware this is happening a child you care about.
I have not read the newer edition, but this book has been updated with content covering cyber-bullying. I can't comment on that other than to say if it's anything like this earlier edition, then I would have to commend it, as I do this one, as a worthy and important read even if you don't think your loved one, or a student in your classroom, is being bullied.