The Appleton-based retailer Book World says it is closing all 45 of its stores, including one in Manitowoc. Company officials say an inventory liquidation sale starts on Thursday. The stores will remain open until the inventory is sold. The company says it has lost customers to the “national shift in the retail marketplace towards e-commerce.” That means it could no longer keep up with Amazon and other online retailers. Book World has stores in Wisconsin, Michigan, Minnesota, Illinois, Iowa, North Dakota, and Missouri. The company says it is currently the fourth largest book store chain in the U-S. Book World has hired Yellen Partners to help with liquidation.