Download the free ebook at THIS LINK
and the ebook will be stored in the Downloads Folder.
If you have iTunes installed follow the suggested procedure.
If you prefer a different App, choose one from the Apple Mac App Store.
I have only seen the "Epub Reader" (with the brown logo)
in action and it seems OK.
The usual controls of Contents, pages Forward
→ and Back ←
and Settings, and Choose another ebook are somewhere.
(Sorry, that's all I know about that.)