How to Read an E-Book
Barnes & Noble makes NOOK for NOOK editions (epub). You can buy a NOOK or download NOOK software, for free, to read NOOK editions on your computer, tablet or smart phone.
Most internet browser software has epub readers you can install as add-ons at no cost to read epub editions.
Adobe Reader can read PDF files on computers, smart phones, some ereaders and tablets.