Book often provide a comprehensive overview or historical background of a subject. They may present theories or expert opinions on a topic. Remember, it is often not necessary to read a book cover-to-cover to make use of ideas presented in it; academic researchers often use skimming and scanning techniques to identify parts of a book relevant to their research.
Ebooks can be accessed through the Library Catalog. Just conduct your search, then use the "Full Text Online" and "Books" links on the left side of the screen to limit to ebooks.
Some ebook packages will require downloading Adobe Digital Editions (free).