Nicene and post-Nicene fathers of the Christian church is an immense work in 14 volumes of early Christian writings. It complements the series on the Ante-Nicene Fathers, we also have here on holybooks.com. Together the writings outline the progress of Christianity through the life and works of the very early Christian scholars and thinkers that led to the foundation of the churches and the great theological controversies of the fourth through sixth centuries. These works have for decades been the standard reference for those interested in the church fathers, the origin of Christianity and history in general.
Download the books here (35-55 MB each):