The Lemonade Wars is a series of books that focuses on a young girl and her brother who decide to have a contest about who can sell lemonade and make the most money.  The book explains how the characters invest in ingredients and supplies, sell products, and divide profits.  

This text could be used in conjunction with a lesson on economics.  In 3rd grade, I observed a teacher who read this text while her classroom focused on raising "money", buying supplies, and producing/selling products that they made.  Examples of products that the students produced were hair bows, home made necklaces, and posters.  The students earned monopoly money throughout the month, managed it to buy supplies from the teacher, and sold their goods to each other.  At the end of the assignment, the students counted their profits.  Along the way, the teacher taught about investments, money management, and quality control.

I believe students in grades 3-6 would enjoy this project and text.