eBooks tend to fall into two categories - those you read cover to cover and those you access to find an answer. You get in, you find your answer, you get out. The second category often includes reference books - dictionaries, encyclopedias, handbook, guides, etc. In this case, you may never see the entire book. Instead, the eBook's search engine will only retrieve the relevant articles or passages identified in your search. This kind of eBook acts more like a database than a book.
Compare the different reading / searching experience of these two eBooks.
An eBook to Read - Uncle Tom's Cabin, by Harriet Becher Stowe.
An eBook to Access - Oxford Companion to World Exploration.