Compiled by William A. Jurgens, I just finished volume 1 of the 3 volume set. "It is a source - book of theological and historical passages from the Christian writings of the pre-Nicene and Nicene eras." Jurgens also did the translation of the writings. It begins with the Didache, then St. Clement of Rome, an Apostolic Father writing about A.D. 80 while he reigned as Peter's 3rd successor as Pope. Volume 1 ends with Pope St. Damasus I, who reigned from A.D.366-384.
I've been reading this as part of my morning devotions. Many of the writings were to fight heresies. There is nothing new under the sun. The same beliefs still exist, it seems. Many people today are so busy making Christ "relatable" they forget His divinity. A few go the other way; so busy with an unreachable pedestal for Christ they forget the Incarnation. Denying either side of Christ is a heresy and anathema. There are so many more heresies that had to be battled. Has the Church weakened? For now no anathemas are pronounced. It would be intolerant. We apparently need to live and let live. Of course, it's a different world. Evangelization is different. Then, the only Christians were Catholic.... No. The Church hasn't weakened. Just gentle as a dove and sly as a fox.
I have been reading this for some time, since I only read and pondered one reading a day. Some were very exciting and I would wish Jurgens had included more in the book ( these are mostly just excerpts of larger works). Occasionally he included pieces so long I would have to break them down. All in all, a satisfactory addition to my devotions.