There are some relatively inexpensive aerobatics reading material to be had that I'd like to recommend. Two books in particular that are very readable and provide just enough information to help you understand how figures are performed, what they look like, and some common errors during their execution. These aren't presented in any order of endorsement; both have their pluses and minuses.
Basic Aerobatics by Mike Goulian and Geza Szurovy covers most of the figures one would encounter in the Primary and Sportsman sequences (these are the two beginning competition sequences). Also discussed in the book are aspects of getting started in aerobatics, e.g., safety, physical conditioning, selection of a airplane and flight instructor. Load limits, stall, developing sequences, and more advanced figures are also contained in this book. Each figure is discussed in sections: Understanding It, Flying It, Common Errors, and If Things Go Wrong. An illustration depicts pertinent portions of the figure, with accompanying photographs from the cockpit of various low and high-wing airplanes. As you may already know, Mike Goulian is an airshow performer, former unlimited competitor, and Red Bull Race competitor. Geza Szurovy is an aviation writer and recreational aerobat. This book retails from $16 - $33, and you can find it used on Amazon.com and abebooks.com.
A new favorite of mine is Duane Cole's Conquest of Line and Symmetry. In this book Mr. Cole writes from the instructor's perspective, introducing us to all the basic figures accompanied with excellent illustrations of each figure, and what some of the errors look like. It's written in a very easy to understand manner. Mr. Cole had a rich history of flying beginning in the 1930's, instructing Civilian Pilot Training Program students, Royal Air Force Cadets, and United States Army Air Force Cadets. With his brothers he formed the Cole Brothers Airshow, was one of twelve people to start the Experimental Aircraft Association (EAA), and started and flew in the Reno Air Races. He ran an aerobatic school for twenty years and wrote nine books. Used copies of this book can be purchased for about $10 on Amazon.com and abebooks.com. I managed to find an autographed copy on eBay for a whopping $6.
Of course these are no substitution for actual instruction with a Flight Instructor in an airplane certified in the Acrobatic category (I feel compelled to offer that disclaimer). There are a host of other books out there. If you find something good, drop me a line and let me know about your discovery.
The weather is warming up, Spring is here, or certainly "right around the corner." I hope to see you out at the airport(s).