Boys on the Brain by Jean Ure
Cresta's diary starts: My mum! She has boys on the brain! This is a fun, pacey diary-based story told through the eyes of a typical contemporary girl of 14 in an 'AB FAB' kind of family.
Cresta and Charlie are seriously embarrassed by their parents who insist on behaving like teenagers... Cresta's mother and her boyfriend play loud music when she's trying to work, and keep her awake at night with their noisy parties.
Charlie, who's a bit plump, complains that her mum keeps nagging her to go on a diet. Hasn't she ever heard of anorexia? she complains.
Cresta and Charlie are serious about their schoolwork and their careers and they are not going to waste their time thinking about boys... at least until they've taken their A levels... But then they meet some seriously cool guys.