The Souls of Black Folk by W.E.B. Du Bois (1903). Du Bois grew up in Great Barrington and this collection of essays — written after he had lived through the South — remains one of the most important books in American history. Reading it before visiting his boyhood homesite gives the place an entirely different weight.
The Berkshire Hills by Clifton Johnson (1895). A Victorian-era account of travelling through the Berkshires on foot, when the hills were farmed rather than forested and the landscape looked very different. Johnson interviewed elderly residents who remembered the revolutionary era, making the book an unusual bridge between worlds.
Berkshire County: A Cultural History by Sarah Cahill Foote (2007). A broad account of how the Berkshires went from agricultural backwater to cultural destination — useful context for understanding why a small Massachusetts town has a world-class orchestra and several major museums within an hour's drive.