Meet Firefighter Ninja! Sometimes, when you rush to help others, you forget to take care of yourself! I race to fires, Big and small, And rescue pets From trees so tall. Life is hard! It's even harder for children who are just trying to figure things out. The Ninja Life Hacks book series is: Geared to kids 4-10+ Perfect for boys & girls Early readers Grades K - 6th grade and up Excellent resource for counselors, parents, and teachers alike Collect the entire Ninja Life Hacks book collection and box sets!.