This year's retreat is going along nicely--weather is cooperating beautifully so everyone can get outside as much as they wish, including for meals on our back patio. The subject matter is interesting: the desert mothers (ammas) of the 4th and 5th centuries. Amazon lists four current books on this subject: The first one, The Desert Mothers by Mary Earle, gives a very quick Q&A on the subject--just scroll down a bit, only takes one minute---it's very good.
The other three are: The Forgotten Desert Mothers by Swan; In the Heart of the Desert by Chryssavgis, Ward, and Ware; and Praying with the Desert Mothers by our own retreat director, Mary Forman.
If you like a little pre-Benedictine monasticism and monastic tales of the desert I think any of the four would be good.