Most puberty books skate around weight gain or can even be openly fatphobic or promote diet culture. This one talks about weight gain as being a natural and healthy part of puberty. It explicitly talks to girls about seeing food as something to nourish their bodies and lives rather than suggesting they should restrict it to maintain a "goal weight." It also does a great job of presenting Intuitive Eating in an age-appropriate manner.
It's for girls 9-14 years old.