"The Hole Thing" is one of the first pinhole books I ever owned. It got me started along a very interesting photographic path. Published in 1974 by Morgan and Morgan, it is a fun, but pretty basic classic for anyone interested in pinhole photography. I love it so much, I bought two copies. BTW a brand new copy of the first edition can set you back more than a few bucks. If you have some money to spend: The Hole Thing : Jim Shull (Paperback, 1974) Otherwise, a good used copy works just as well.
I'll be adding posts about pinhole over the next month or so and until WPPD. http://www.pinholeday.org/
I talk about pinhole and zone plate photography in my book too. Buy my book here: Rethinking Digital Photography.