Looks like you're using an embedded browser inside an iOS app. (Maybe you followed a link from a social media site?)
To read this ebook you should open this page in safari, or use one of the "One-click" buttons, above.
Not on iOS? Try the instructions for Android, desktop computers, or ereaders (Kindle, Nook, Kobo, etc.).
You may already have an app which reads ebooks. Download the epub file and see if you're offered an option for opening the file. If so, you're done! If not...
iBooks
Marvin is a great way to read ebooks.
So is Aldiko.
Not on iOS? Try the instructions for Android, desktop computers, or ereaders (Kindle, Nook, Kobo, etc.).
You may already have an app which reads ebooks. Download the epub file and see if you're offered an option for opening the file. If so, you're done! If not...
Aldiko
Not on Android? Try the instructions for iPhone/iPad, desktop computers, or ereaders (Kindle, Nook, Kobo, etc.).
Calibre
Not on a desktop computer, or want to "side-load" ebooks onto a device or app? Try the instructions for iPhone/iPad, Android, or ereaders (Kindle, Nook, Kobo, etc.).
Not using an ereader? Try the instructions for iPhone/iPad, Android, or desktop computers.
Dropbox is a good way to share your ebooks between desktop, tablet and smartphone. If you see a dropbox button above, click it to load your books into your dropbox folder. Then load the file into your reader application on your device.