Normally, you wouldn't think of an e-book as something that is purchased in any particular physical location, but in fact, there are several Davis-specific ways to obtain e-books.
Or, you might be interested in books in general.
You can purchase e-books from the Avid Reader through Google e-books; see the Avid Reader website for details.
The UCD Bookstore offers e-book textbooks (although unfortunately, these can be almost as expensive — or in some cases even more expensive — than the paper copies).
E-books can be read on most modern computers, smartphones, and tablets. Specialized e-book readers are also available. E-book readers (or simply e-readers) often attempt to simulate the appearance of a traditional book page by using e-paper technology. Target and RadioShack sell the Barnes & Noble "Nook" line of e-readers. The Tech Hub at the UCD Bookstore sells iPads.