Forerunners and Rivals of Christianity: Volume 2: Being Studies in Religious History from 330 BC to 330 AD by F. Legge
Originally published in 1915, this book contains a survey of the origins of Christianity and the impact that other religions had on its formation. Volume Two covers post-Christian pagan religions such as the Mithraic cults and Manichaeism, as well as heresies such as that of Marcion. This book will be of value to anyone with an interest in ancient religion and the development of Christianity.