Convenience and Portability
You can carry a library full of books in the space taken up by a notebook. I'm constantly amazed by the amount of information available, held in a space no larger than that of a steno pad, and summoned with the tap of a finger.
After locating a suitable book all that's necessary might be a couple of clicks and a coupl of minutes. All done from the comfort of your cab or comfy chair.
The Internet Bonus
Some eBooks are sold with bonus information not available in a print copy. In addition, if the book you choose is a historical novel, biography, auto-biography or some other non-fiction book there may be links to Internet sources included in the text or appendices. If you're using an eBook Reader, connected to the Internet, like the Kindle Paperwhite, you'll be able to follow the links and gain far more information than possible in a printed work.
Find words or phrases at the speed of light. How many times, whether you're reading a novel, textbook or...whatever, you need to reference a previous passage? You can remember the line, approximately where it is but you've got to thumb through all the previous pages. No more, finding that word or phrase can be done quickly and easily. What once was difficult and tedious is, now, a quick and simple task.
You might think the ability to highlight, index and reference particular passages in a book might only be useful to a student reading a textbook but, believe me, if you're utilizing your downtime in an effort to further your education you'll find this feature more than a little helpful. One of the most important books on economic theory, accessible to the layman and written in the 20th century, is Capitalism and Freedom by Nobel Prize winner Milton Friedman. I read the printed version and found myself highlighting and notetaking all the way through; that wouldn't have been an issue with the eBook version.
Employing WhisperSync it's possible to listen to an AudioBook while you're driving and, then, continue reading the eBook version when you wander into a restaurant for dinner. WhisperSync will allow you to pick up, in the eBook eBook version, where the Audible Audiobook version left off and vice versa. Amazing.