The Rule of Three
Fun and entertaining second book in the Sisters Club series. Totally worth the read.
Continues in the same style as the first.
Cloudy with a Chance of Boys
While I really loved this one, I do think the target audience is just a little older, so I wasn't sad that Boo wasn't interested.
This very cute installment (again, same style) has a lot to do with boys, obviously, and figuring out what a crush means. Since Boo's not there yet, I don't know what she'd think really.
Really a great book for girls in later elementary and middle school.