Indispensable handbook of mileages between features and facilities on the AT Known as the bible of Appalachian Trail hiking," the Appalachian Trail Data Book consolidates the most basic information from the 11 official ATC guidebooks into a lightweight table of distances between the major AT shelters, road crossings, and features. Divided to align with the guidebook volumes, the Data Book is updated each December to address trail relocations, new or removed shelters, and other changes. In addition to including codes for lodging, food, water, and other essentials, the Data Book is keyed to both the individual guidebook sections and the separate maps."