Ebooks, also called electronic books, digital books, or online books, can be accessed 24/7 from any location.
Ebooks allow one to search the full-text of the books, which can be both advantage and a disadvantage.
Image source: Tomormarusan. Kyoto National Museum, Main Gate. Wikimedia Commons, GFDL.
If you're looking for a piece of information on a narrow topic within a book, this can be a huge advantage.
If your topic is broad, however, you'll drown in results with a full-text book search. If this is the case, consider limiting your search to the title field.