In addition to St. Maximus’ 400 Chapters on Love, Mr. Granger also recommended for those who want something “less monastic” than the Philokalia, The Evergetinos. Goarch.org says this (and other good stuff) about it:
“The Evergetinos is probably the beginning point for Orthodox in the West who wish to capture something of the essence of their faith. If the Philokalia teaches pure prayer and the path to deification and union with God, the Evergetinos provides us with anecdotal evidence that the practice of Christian virtues, such as humility, chastity, love for our neighbor, and submission to the will of God, can bring us to the brink of the ultimate encounter with the divine by which we are elevated to the philosophical and higher struggle for perfection. If from the Philokalia we are instructed in the philosophical way to perfection, in the Evergetinos we are guided to the pragmatic life of humility and self-control (composure), the indispensable requisites for the more advanced endeavor of the former. In the Evergetinos we see the virtuous lives of the desert monks who, during the first few centuries of Christianity, fled to the barren deserts around the Mediterranean and lived the most extreme and awe-inspiring lives of asceticism in a search for God.”
Here’s a compelling write-up about it with excerpts.