GirlHacks is a cool book full of really great tips for preteen/teenage girls written by two 12 year old friends: Topanga Skye Corso and Catia Mehring. The girls were inspired to write the book because they wanted to share ideas that have made their lives easier and more fun. Topanga and Catia share fun tips on everything from What to do at a sleepover to Cool ways to decorate your room from Technology tips to Fashion advice . $1 from the sale of every book will be donated to international charity Free The Children, an organization committed to delivering a sustainable development model that empowers people to transform themselves, their families, their communities and the world.