Eusebius 
History of the Church from Christ to Constantine [EPUB ebook] 

Eusebius’s account is the only surviving historical record of the Church during its crucial first 300 years. Bishop Eusebius, a learned scholar who lived most of his life in Caesarea in Palestine, broke new ground in writing the History and provided a model for all later ecclesiastical historians. In tracing the history of the Church from the time of Christ to the Great Persecution at the beginning of the fourth century, and ending with the conversion of the Emperor Constantine, his aim was to show the purity and continuity of the doctrinal tradition of Christianity and its struggle against persecutors and heretics.