Apple computers and ipads
Should be able to read ePub files using their iBook application.
PCs may need to download and install an ePub reader. There is a well-known free reader called ICECREAM (for Windows XP, VIsta, 7 and 8) downloadable from http://icecreamapps.com/Ebook-Reader/
Downloads from this page directly onto some mobile devices not yet available.