An Introduction to 2009 Lincoln Cent Errors, By James Porter, is officially my new favorite book on coins. It covers everything about the 2009 doubled die errors, from reverse to obverse, Birth and Early Childhood to Presidency. The book starts off with an introduction, and then continues to explain a little bit about what makes a doubled die, and why this is a good (In my opinion GREAT) series to collect. It then takes off, with the largest, and my favorite chapter, about all of the Formative Years doubled die reverses. Then it goes onto the Early Childhood and the Professional Life and Presidency reverses. It then describes the characteristics of some doubled die reverses, which was very helpful. He then provides his records of purchased 2009 coin rolls, and what errors he found in them. If you have any interest at all in 2009 coin errors and varieties, then you should buy this book. It is good for the advanced collector and the beginning collector!