“Earthen floors are ubiquitous in most of the world. They are the most accessible type of flooring to a vast portion of the human population. In the modern world earthen floors are still something of an oddity to most people, that is until they step foot on one. And then they are hooked for life.
As a simple mixture of sand, clay, water and fibers, more and more people are installing them in their new modern homes with stunning results.
Today’s practitioners of earthen floors are able to create extremely beautiful, deeply rich wearing surfaces in our most refined spaces. The techniques used to accomplish such enjoyable surfaces have been honed through trial and error by a handful of people who readily share their knowledge. Any modern home being built today with natural fibers or earthen walls should also include earthen floors. The durability and applicability are on par with any other flooring system, and we are surprised no one has really covered this topic in a comprehensive way, until now.”
More at the source: The Last Straw
This seems like the best book on the subject, judging by the rave reviews at Amazon.
Bill and Athena published a booklet called Earthen Floors quite a few years ago.