Can anyone recommend a book on sex, relationships, consent etc for my 12/13 year olds?

[sandyballs]

I do talk to them about these issues but they get embarrassed or walk out the room. Lately I've chipped away at issues in the car where they can't escape but I think it would be very useful for them to have a book appropriate to their age. They've got younger ones but nothing for teens.

[MsIngaFewmarbles]

If it's girls can I recommend The Rough Guide to Girl Stuff. Excellent guide to puberty, relationships, contraception, feelings and families.