After you have generated your results list in Summon, look at the left margin column to select the options for filtering your results. Your original results list will likely contain sources that are books (print and electronic), journal articles, newspaper articles, magazines, streamed media, etc. If you are interested in focusing your results to only books, choose the "Book/Ebook" option to filter your results to only that type of source.
The RIT Library has a continually growing collection of e-books in a diverse range of subject areas. You can easily locate e-books using the refinement filters within Summon. Conduct your Summon search, refine your search to "items with full text online" and limit the content type to "Books/ebook". Your list of results will now be only e-books.