Each Friday in an event called Nook's Free Friday, Barnes and Noble offers a specific book for downloading at no cost. The selection is a book for which customers must pay on any other day.
The book is free only for that one day and is unlikely to appear again at no charge. The Nook Blog lists the promoted book each Friday.
Also as a part of Free Friday promotions, Barnes and Nobles offers a free app. Past selections include "Civiballs," a puzzle adventure that takes the user through the Roman, Viking and Incan civilizations in search of ancient artifacts, and "Car Dentist and Wash," a child's app that takes place in a virtual car shop.