Reddit reviews Niwaki: Pruning, Training and Shaping Trees the Japanese Way

http://www.amazon.com/Niwaki-Pruning-Training-Shaping-Japanese/dp/0881928356

Here is a pretty good book in English about niwaki specifically. I think you're right that there is an aspect that is meant to seem effortless but the amount of work that goes into just the pruning is incredible. And everything is placed, the rocks weren't just found there. There are all sorts of symbolic arrangements to those too, like they bury them halfway, again to give the impression that it's very old. Now a lot of those gardens actually are very old but really not left up to chance that much. It's like a whole art form that we barely have in the west but there are some Japanese style gardens here.