Climbers' Guide to the Great Falls of the Potomac
This is the guide to own if you are going to climb in the Great Falls area. It covers crags on the Virginia and Maryland side, over 30 in all, and discusses more than 300 routes ranging from 5.0 to 5.13.
The book has good photos that allow one to locate individual routes.
There are sections on regulations, ethics, safety, geology, and history as well.
One of the best things about the guide is its small size; it is light and easy to carry in a side pocket of a pack, from which it is easily retrieved without needing to take the pack off.
The book retails for about $13.