My main research is in the areas of Pentecostal history and intercultural theology. I am currently working on the relationship between Pentecostalism and African popular religious ideas, and recently published a book on this subject. I have also published a book on Pentecostalism in the global South in the prestigious series Oxford Studies in World Christianities. I have written nine monographs on African Christianity and global Pentecostalism, the latest being Spirit-Filled Word: Religious Dis/Continuity in African Pentecostalism (Palgrave Macmillan, 2018), An Introduction to Pentecostalism: Global Charismatic Christianity, 2nd ed (Cambridge, 2013), To the Ends of the Earth: Pentecostalism and the Transformation of World Christianity (Oxford, 2013), Spreading Fires: The Missionary Nature of Early Pentecostalism (SCM & Orbis, 2007), African Reformation: African Initiated Christianity in the Twentieth Century (Africa World Press, 2001), and Zion and Pentecost: The Spirituality and Experience of Pentecostal and Zionist/Apostolic Churches in South Africa (Unisa Press, 2000).
I have co-edited and written a chapter in Studying Global Pentecostalism: Theories and Methods (University of California Press, 2010); edited (with Walter J Hollenweger) and written three chapters of a volume entitled Pentecostals After a Century: Global Perspectives on a Movement in Transition (Sheffield Academic Press, 1999). With Edmond Tang, I have edited a volume on Asian Pentecostalism entitled Asian and Pentecostal: The Charismatic Face of Asian Christianity 2nd ed (Regnum, 2011).