The book Mystics & Zen Masters, mentioned earlier, is good, discusses existentialism. I remember reading this (and several others by him 8,9 years ago and enjoying it, thinking that (a the time) I liked his application of existentialism. He goes into Kierkegard (a Christian existentialist philosopher) and others.
But I disagree with nomescreed202 - I believe he was sincerely living a life of contemplation, searching, too, regardless of one's thoughts on Christianity, Cathlocism, etc. (He was living a very simple life of quiet. Surely, for the most part, his spirit was evolving faster than ours on the interstate.) And thus, he stumbled on Thich Nhat Hahn and the likes, who he said he had more in common with than most Christians. I don't belong to a religion, but an obvious line that's drawn that can at least make one tolerant of a religion, is whether or not they condemn other religions. Merton was happy after the (big Catholic 'decide what's right and wrong' - diocese?) meeting in the 40s that announced a new stance towards other religions - one of tolerance.
And Erika, no. The quest for publication isn't any more an attempt to glorify the self than 'I'm not going to publish because it's vain self-glorification.' The ego equally strengthens itself with the latter stance.