What they are: Long pieces of writing on one topic, usually divided into pages and (sometimes) chapters.
What they give you: A broad, detailed look at a topic. If the book is scholarly, it will also give you citations to other sources.
How to spot them: Both books and ebooks have publication information, including the name of the publisher and the year of publication. Look for this info on the copyright page near the beginning of the book.
What they look like in library search results:
What ebooks look like: (Note the publisher and copyright.)
What books in print look like: (Note the publisher and copyright.)