I looked and looked but couldn't find it online. it was just called Zen Buddhism but the author had a very western name. The book had a pretty big impact on me but not in a religious or hooky "one with the cosmos" sort of way. More like it just sort of clicked with me, which is as good a description of the concept as any really. I may still have the book somewhere, if I find I'll post it here.
Just seconding my interest in the book, if you manage to find it. Perhaps you could ask your friend if he remembers?