|The Ladder of Divine Ascent - Icon at St. Catharine's Monastery, Sinai|
Unfortunately, it is relatively expensive; the best English translation by Metropolitan Kallistos Ware, consisting of five volumes, will set you back significantly more than most high quality study bibles. It is also a formidable volume, as thick a read as the Bible itself. What a pity more Christians cannot read Koine Greek and Aramaic, in which it and the Gospels were originally written, and thus have access to it free of charge.
However, if you cannot afford the Philokalia, in all its splendor (and it is something worth saving your pennies for, or borrowing from the library), there are two related volumes that will provide you with much of the same guidance, that have translations that are, in the United States, in the Public Domain, and can thus be downloaded free of charge over the Internet.
One is The Ladder of Divine Ascent, by St. John of the Ladder, a monk whose life is shrouded in obscurity, but whose book is highly prized by monastics. Read in the Orthodox church during Lent, it outlines the journey of ascetic purification made by monks in the ascetic life, but is of equal value to those living in the world. One might think of it as The Philokalia In a Nutshell.
The other, published 102 years from the Philokalia's initial 1782 release on Mount Athos, is work, which most likely is a fiction inspired by the lives of several Russian ascetics, but which could be a genuine biography or autobiography, entitled The Way of the Pilgrim, which chronicles the spiritual progress of a man who seeks to follow literally the admonition of our Lord to "Pray without ceasing." This he accomplishes, following the guidance of a monk, with the help of a prayer rope, the Philokalia, and the Jesus Prayer, which he says tens of thousands of time a day; in every waking moment, until he attains in due course the unceasing prayer of the heart. Imbued with incredible spiritual energy, he then happily lives as a wandering hermit, in complete trust in our Lord, with only his Philokalia and Prayer Rope. As a work of pious literature it is unrivalled, and it contains within much of the common theme of the Philokalia. It should be noted however that the protagonist attains the unceasing prayer of the heart in an unusually short amount of time; although my ascetic discipline pales in comparison with that of the nameless pilgrim, I have yet to attain it, and may never, for many monks of rigorous discipline, the attainment of such a state of grace is the work of a lifetime.
Nonetheless, the words of the 20th century Chicago ad mogul Leo Burnett come to mind: "Always reach for the stars. You might not get there, but you won't wind up with a handful of mud, either."