classics of Apostolic Fathers

J. B. Lightfoot, The Apostolic Fathers, 5 vols. (London:  Macmillan, 1889-1890).
Part 1, vol.1 ; Part 1, vol.2 ; Part 2, vol.1 ; Part 2, vol.2 ; Part 2, vol.3
Abridged version

"Still unsurpassed, however, for all serious scholarly on these texts" -Larry Hurtado (source)