On a computer
If you do not have a device, you can use one of a few programs on your computer to view your ePub file.
If you are running the latest version of OS X, the best program to use for viewing your eBook is iBooks for Mac. This desktop version of iBooks comes pre-installed in OS X Mavericks, so there is no need to install it separately. You can also run iBooks on earlier OS versions of Mac It’s a free download but iTunes will ask for credit card information anyway. Don’t worry, it’s still free.
The most common program people use when looking at ePub files on a computer is Adobe Digital Editions (ADE). To install the ADE software on your computer, visit the ADE website, then download and install the program. It’s easy and fast. When the program opens you can choose to register it with an Adobe account, or you can leave it unregistered. To open your ePub file, you can either double click on the file (ADE installs as the default ePub reading program on your computer) or click on the Library dropdown and select Add item to Library.
For other computers, the most up-to-date program, and the one recommended is the Readium plugin for Chrome. You must have the Chrome browser installed in order to use Readium.
In iBooks on an iPad
If you have an Apple iPad/iPhone/iPod Touch, you can view your ePub file in a variety of software applications on the device. The most important app to view your file in is the iBooks software from Apple. If you do not have iBooks installed on your iPad you can download it for free from the iTunes App Store. Once iBooks is installed, you can add the ePub to your iTunes library choosing File > Add to Library, or drag the ePub file to the Books library in iTunes on your computer.
Note that all images, including charts, can be enlarged by double-clicking.