If you have any device (tablet, smartphone, e-book reader, notebook, table-top, etc.) except for Amazon Kindle, – will be right out to take EPUB.
EPUB is a technical standard for e-books, can be read, for example, by the Kobo eReader, BlackBerry devices, Apple’s iBooks app running on Macintosh computers and iOS devices, Google Books app running on Android and iOS devices, Barnes & Noble Nook, Amazon Kindle Fire, Sony Reader, BeBook, Bookeen Cybook Gen3 (with firmware v2 and up), COOL-ER, Adobe Digital Editions, Lexcycle Stanza, BookGlutton, AZARDI, FBReader, PocketBook eReader, Aldiko, CoolReader, Mantano Reader, Moon+ Reader, the Mozilla Firefox add-on EPUBReader, Lucifox, Lucidor, Okular and other reading apps.
MOBI is a specific Amazon Kindle format.
I would like to take this opportunity to note, that using gadget witn monochrome display for my photobook reading is a bad idea.