I am currently reading "Prayer" by Hans Urs von Balthasar. In my opinion, if not the best, then at least the most comprehensive book on prayer I have read. Make no mistake, this is not an easy read by any definition of the word. I had to keep the old Websters handy as I read this. It is also sometimes a bit hard to read simply because I am a protostant. Balthasar at times is extremely critical of the Protostant tradition. ANd yet even while being critical, he makes some very valid points that if we as protostants will listen to, we can learn from.