'Derry~Londonderry: A Walk Around the Walled City' by Richard Doherty & Tim Webster

This book divides into two sections.  The first part (green pages) is a guided walk around the city walls.  Now 400 years old, these walls tell an eventful, sometimes violent, story about the city.  The second part (blue pages) is a short history of the city from antiquity to the present day.