In Alex Archer's previous journal, Star Jumper, he revealed how his amazing cardboard spacecraft was tragically destroyed during a pillow fight with his little brother Jonathan. Alex knows that all geniuses encounter a setback now and then, yet this setback has only spurred him on to even greater achievements. Alex's new spaceship is twice the size of the old one and is equipped with many astonishing features, such as a telescope that can see around the universe and an electromagnetic shield stronger than Superman's cape! But will Zoe Breen want to be Alex's co-pilot when he leaves Earth and goes galaxy-hopping? And what about Alex's rotten little brother? Does Jonathan really want to drive Alex stark-raving mad? Or is he just looking for some big brother attention? Find out the answers to all these questions and more as the cardboard genius unleashes his brainchild --- the Gravity Buster --- and defies the laws of physics! But who will bring him back down to Earth?