His first book on Italian colonialism in Ethiopia is The Plot to Kill Graziani (Addis Ababa University Press in 2010), an analysis of the assassination attempt on
Rodolfo Graziani that took place on 19 February 1937. The Plot to Kill Graziani was declared Ethiopian Book of the Year by
Richard Pankhurst,[4] presented by the
Ethiopian Broadcasting Corporation,[5] and featured in Eland's travel series, Ethiopia Through Writers' Eyes[6].
His second book, The Massacre of Debre Libanos (AAU Press, 2014), reports the massacre of members of the Ethiopian Coptic Church in the monastery village of
Debre Libanos in Italian East Africa between 21 and 29 May 1937. Campbell's findings were featured in the Italian documentaries Debre Libanos[7] and If Only I Were That Warrior.[8]
His third book is The Addis Ababa Massacre (Hurst, London & Oxford University Press, New York, 2017), an account of the atrocities following the attack on
Rodolfo Graziani referred to as
Yekatit 12. The book got recognition from a spectrum of international reviewers,[9][10][11] and in 2018 became available in an Italian edition, Il massacro di Addis Abeba (Rizzoli, 2018), raising a debate in Italy about the responsibilities of Italian colonialism.[12][13][14][15]
In 2022 Campbell published Holy War: The Untold Story of Catholic Italy's Crusade Against the Ethiopian Orthodox Church (Hurst).[16] In the book Campbell uncovers the involvement of the Italian Catholic Church in facilitating
Mussolini's invasion of Ethiopia, highlighting the complicity of key figures within the Vatican hierarchy, including
Pope Pius XI, Secretary of State Eugenio Pacelli (who would later become
Pius XII), and the archbishop of Milan
Alfredo Ildefonso Schuster. The work was named one of the best book of 2002 by the American 'Foreign Affairs'[17] and obtained wide acclaim from a range of global critics.[18][19]