There are over 300 letters of Basil of Caesarea preserved, and these 4 volumes give the Greek and an English translation. Internet Archive also has the later publication of some of these letters (English only) in the Fathers of the Church series. These letters give a wonderful insight into conditions in Cappadocia (now eastern Turkey) in the late 4th century AD. Reading them transports one to a different place and time. Yes, it will take time to read through 4 volumes, but it is well worth the effort. Incidentally, for those who are not familiar with Basil and wish to know about him before jumping into the letters themselves, I highly reccomend P. Rousseau, Basil of Caesarea, University of California, 1994. This book is an excellent study of Basil and his times. Again, these letters are 4 volumes of good reading.