Happy Fair Use Day, which was apparently today or yesterday. It’s tough keeping track while living a day ahead of what I’m used to. (Link)
This is §107 of the U.S. Copyright Act, which provides a for exception to an author’s exclusive rights that come with copyright. Fair Use is generally what allows you to reproduce limited amounts of an author’s work for “purposes such as criticism, comment, news reporting, teaching, scholarship, or research” without infringing on an his copyright.
Be careful, though. If you use the “heart” of the author’s work (E.g. – A passage from a book that is so compelling as to be the only reason to buy the book.) then you could be found to be infringing.