For those without a Kindle or Nook or other such e-reader, do not despair. You can download for free the computer version from Amazon or Barnes & Noble and read e-books on your laptop, via the "Kindle for PC" and the "Nook for PC" options.
P.S. Then when you purchase books therefrom, your e-book selections should be for the PC reader and another window post-purchase will connect you to your computer-resident collection. Thereafter, you can access your library of e-books via the icon that will appear on your desktop.