When talking about Cob the best resource is The Hand-Sculpted House. The limitation with a book is you do not get your hands into the cob. Reading about cob does not free you, making it and sculpting it frees you. At a workshop I attended one of the participants could not get enough making cob and thinking about all the things he could do with it. Cob is simply sand, clay, and straw, but with it so much can be made. It is in the simplicity that is liberating. You can learn how to make cob and can literally make it from the ground you stand on. The soil you already own. Sure, bringing in good masonry sand and nice straw will make it better, but most people on land can make it with what they have.