Who is Richard J. Foster from Celebration of Discipline and what is their importance?

Richard J. Foster is the author of the book Celebration of Discipline: The Path to Spiritual Growth, which Christianity Today placed on its list of the top ten books of the twentieth century. This is his first book, and at the time he writes it he is a Quaker pastor. He went on to write many other best selling books. Mr Foster is also the founder of a church renewal movement and is editing a study bible.