Travel and history
A Concise History of Bulgaria by R.J. Crampton (Cambridge University Press) — the standard English-language history, updated to the post-communist period. Covers the Ottoman era, the National Revival, the communist decades, and transition with clarity and no sentimentality.
Beyond Hitler's Grasp: The Heroic Rescue of Bulgaria's Jews by Michael Bar-Zohar — the remarkable story of how Bulgaria, alone among Nazi-allied states, refused to deport its Jewish citizens to the death camps. Essential reading for understanding both the wartime period and Bulgarian national character.
The Bulgarians in the Seventeenth Century by Dennis P. Hupchick — an academic look at Orthodox society and culture under Ottoman rule; useful background for understanding the monastery system and the National Revival movement.
Fiction and memoir
Under the Yoke by Ivan Vazov — the great 19th-century Bulgarian novel, set during the April Uprising of 1876. Melodramatic by contemporary standards but still readable, and central to understanding how Bulgarians see their own history.
Street Without a Name by Kapka Kassabova — a memoir of growing up in communist Sofia and returning as an adult. Funny, sharp, and unsentimental about both the communist past and the chaotic transition years.
Music
May It Fill Your Soul: Experiencing Bulgarian Music by Timothy Rice — an ethnomusicological study of Bulgarian folk music that manages to be engaging for non-specialists. Bulgarian polyphonic choral music, with its unusual rhythmic structures and microtonal harmonies, rewards some background reading.