For nearly three centuries, Christianity grew in the shadow of the Roman Empire at a pace that continues to astonish historians. Estimates suggest that the early Christian movement expanded by roughly forty percent per decade during its first three hundred years , despite lacking political power, social privilege, or military protection. The Forty Percent Church tells the story of how this unlikely community endured and grew in a world that often opposed it. Drawing on Roman historians, Jewish sources, early Christian writings, archaeological evidence, and modern scholarship, Jason Conrad reconstructs the first three hundred years of Christianity from 47 BC to AD 311 , tracing the movement emperor by emperor, crisis by crisis, and witness by witness. At the heart of this history stands the conviction that Jesus Christ truly rose from the dead. That belief reshaped worship, ethics, allegiance, and courage in ways no empire could suppress. Early Christians held a unified core of faith while allowing diversity of practice, forming resilient communities capable of crossing cultures without losing their identity. Their moral distinctiveness, sacrificial love, intellectual engagement, and confidence in the life to come transformed cities and confounded critics. This book explores why the earliest Christians grew so rapidly, how they endured persecution, how they cared for the vulnerable, how they defended their beliefs, and how their way of life became a living testimony to the power they proclaimed. Written for readers interested in early Christianity, the Roman world, and the historical foundations of Christian faith, The Forty Percent Church offers a deeply researched and compelling account of one of history’s most extraordinary movements.