What a wonderful book!
What some may not know, is that Father Jean Corbon, a Melkite Dominican of blessed memory, also authored the fourth section of the Catechism of the Catholic Church. Much of the theology of the role of the Holy Spirit in the Divine Lirtugy was also authored by him as well.
Then Cardinal Ratzinger and Chrisoph Schornborn wanted a theologian from the East to write the section on prayer and Corbon was an excellent choice. Wellsprings is already a spiritual classic. And, interestingly enough, I am reading it right now!
God bless,
Gordo