DD absolutely loves these books and keeps reading them again and again. I'd previously looked at a few pages and it seemed all pretty harmless.
However, I actually read a few days ago the first chapter of the first book and it talks a lot about "getting girls". Nothing super inappropriate but just stuff about what the protagonists thinks will get you girls. By getting I think he means impressing girls or making them like you. I know a lot of teenagers will think like that (and certainly me and all of my friends did as teenagers) but in retrospection I do think it's quite a stupid and sexist notion that you should change your behaviour or do something to impress the opposite sex in particular. If DD was a teenager then she would have come across this stuff else where anyway but not as a 7 year old?
Also, is there anything else that's not age appropriate in the book? Or any other outdated stereotypes or attitudes it perpetuates?
DD has already read the entire first series (several times) so there's nothing I can do about that anymore but maybe I should vet more carefully what she reads from now on.