The war start because Jessie skips 2 classes and are joining Evan (her older brother's) class after the summer holiday. Evan makes a Lemonade Stand because he want's money for an iPod. He and his friend Scott pair up and Jessie asks if she can join. They of cause say NO and she then makes her own Lemonade Stand whit Megan, a girl from Evan's class. Now the war is on.
I loved the book because of all the sibling drama. Jessie is so smart and Evan is annoyed of her brain.