Far and away the most intelligently written, realistic portrayal of being 15. I read this as a teenager and years later can still read it utterly gripped. The characters are just so memorable. If you've ever felt like a misfit - or have a daughter who feels like one, give her this book. If you ever feel like your teenager is sneering at her family or telling lies - give this to her. If you ever want a reminder of how things seem from the other side - this book is for you, not just your daughter.
I have a degree in English Literature, and have read many lofty works - this book for teenagers remains one of my favourite books, and on re-reading it as an adult, it has not diminished in power. It's only competition is Izzy, Willy-Nilly - which is a book of such depth as you would never guess by the title!