Subtitle: A low-cost, wood-fired, mud oven, simple sourdough bread, perfect loaves.
It's a nice combination of making it an experimental, hands-on, try-and-fail-and improve task for non-bookish people, and providing pointers to more specialized knowledge useful for planning complicated better ovens. I approve of the soil texturing and settling experiments.
I'm also really impressed that they seriously discuss efficiency, and the Jeavons 'efficiency trap', and why alternative oven designs might be a better use of fuel if you can't do an enormous, carefully sequenced amount of baking with each firing. (Which means your bread has to keep, if you're baking for only a few people which probably means adjusting the recipe; one extreme being, I should think, Swedish rye crackers, which have the hole in the middle so they can be stored on a pole to keep dry between their infrequent bakings.)
Find in a Library: Build your Own Earth Oven