BookScan is a service that tracks book sales across various retailers in the United States. It collects data from both physical and online bookstores, providing insights into which titles are selling well and how many copies are being sold. This information is valuable for publishers, authors, and retailers to understand market trends. The data collected by BookScan is often used to create sales rankings and reports, helping industry professionals make informed decisions about marketing and inventory. By analyzing this data, stakeholders can identify popular genres, emerging authors, and shifts in consumer preferences.