I'm a fan of, by Joe Kissell. It's a $10 ebook that is specifically designed for beginning command line users on Mac OS X. I think it's exactly what you asked for. I find many O'Reilly UNIX books to be frustratingly opaque for the beginner. Book blurb from the above link: If you've ever thought you should learn how to use the Unix command line that underlies Mac OS X, or felt at sea when typing commands into Terminal, Joe Kissell is here to help! This 111-page ebook will help you become comfortable working on the Mac's command line, starting with the fundamentals and walking you through more advanced topics as your knowledge increases. And if you're uncertain how to put your new-found skills to use, Joe includes numerous real-life 'recipes' for tasks that are best done from the command line.
Disclaimer: Though I wrote a seven years ago, I have no financial interest in Joe's book.