Peter Carney and Meri Anastassova   Bulgaria: the Mountain Resorts (Bulgaria, PMC). Useful guide to the highland regions, written by a Sofia-based team and full of insightful nuggets. On sale from bookshops and kiosks in Bulgaria, as are the same authors' Bulgaria: Sofia and Plovdiv and Bulgaria: the Black Sea Coast .

Julian Perry   The Mountains of Bulgaria (UK, Menasha Ridge Press). No-nonsense practical guide to trekking routes in the Balkan, Rila, Pirin and Rhodope ranges, written by an experienced trek leader. A good investment if you're planning a major hiking expedition.