"Seller Book" is a sales management application tailored for individuals engaged in buying and selling through the Flea Market app. Developed in collaboration with Flea Market sellers, this app simplifies sales tracking by enabling easy input and visualization directly on smartphones. With features like real-time sales management, graphical representation of sales, costs, and profits, and user-friendly smartphone UI, Seller Book eliminates the need for traditional sales management tools like Excel.

The app offers both a free plan with basic sales management functions and a paid plan for enhanced features. The paid plans include the Product Master for comprehensive item handling and the Premium Plan for data synchronization across multiple devices. Seller Book also provides auto-renewing subscriptions and detailed cancellation instructions for user convenience.