Allow me, please, to quote from the introduction to the first volume of the English translation (which was done by G.E.H Palmer, Philip Sherrard, and Kallistos Ware).
The Philokalia is a collection of texts written between the fourth and fifteenth centuries by spiritual masters of the Orthodox Christian tradition. It was compiled in the eighteenth century by two Greek monks, St Nikodimos of the Holy Mountain of Athos (1749-1809) and St Makarios of Corinth (1731-1805) . . . .
The work itself has gone through several Greek editions after the first one in 1782. In 1893, it was reissued with the addition of some works on prayer written by Patriarch Kallistos. And finally, a "third edition, in five volumes, was also published at Athens during the years 1957-1963 by the Astir Publishing Company." It was first translated into Slavonic--it is most likely this translation which the anonymous monk of the spiritual classic The Way of the Pilgrim (which may be most familiar to Western readers by its mention in J.D. Salinger's short novel Franny and Zooey)--and then later into Russian.
The Philokalia--the word in Greek means "the love of the beautiful," and it is this love, the love of God and the love for God, that it tries to instill in its readers, along with a "pure hatred" of the things of the flesh--which is not, that is to say, of the body--the Church Fathers represented draw the same distinction as St Paul the Apostle, that by "flesh" is meant the fallen aspects of humanity and by "spirit" those that are purified to be back in alliance with the original plan of God. And like St John Climacus in The Ladder of Divine Ascent (which is usually read during Lent at most Orthodox monasteries), the Fathers of the Philokalia are very careful to remind us the advice they give is also for those in the world, not only for those within the asceticism of monastic life--"the way of affirmation and the way of negation," as the abovementioned Kallistos Ware writes in one of his own books, The Orthodox Way.
The Philokalia is one of the principal works of the hesychist movement, which is extremely widespread in the Orthodox world, particularly in monasteries. This is the way of stillness, of continually calling on the name of God--the preferred method is with a short "arrow prayer" called the Jesus Prayer: "Lord Jesus Christ, Son of God, have mercy on me, a sinner." There are variations, but this is the usual form. The Philokalian Fathers preach this unceasingly as a very effective means of contemplation.