Barnes & Noble offers a free ebook through their Free Fridays program, as of September 2015. The Free Friday book is posted on the Nook blog and the Nook Facebook page and is available for free downloaded only on the Friday it is featured.
Though the books are completely free, a credit card is required for verification purposes in order to download them.
Barnes &Noble has been giving books away on Free Fridays since 2010. Books such as "Wicked" by Gregory Maguire, "Shiver" by Maggie Stiefvater, "The Midwife's Here" by Linda Fairley and "Buddha" by Deepak Chopra have been featured as part of this program.