14 Hard Questions for Libertarians: Answered is an excellent resource. Where reading Rothbard and thinking things through from first principles (fundamental economics, the NAP, etc.) will inevitably produce the same or similar answers to those in this book, it is an amazingly simple and accessible resource for beginners, people who can't be bothered making freshman-level arguments with detractors, and people who may have done all the heavy lifting themselves and may have a couple blind spots.
I, personally, land in all three categories. I'm an anarchist of only about two years, and I have a lot of catching up to do, I've already cited and linked to this book twice on facebook in arguments with people that are intelligent but ignorant, and was surprised to find myself reassessing some of my stances on things. Most especially my position on Prisons in a Free Society has come into question, and I've been inspired to do more reading in primary sources and more critical thinking about how I arrived at my position. I expect to make a full blog post in the future, once I'm done researching and revising my position.