Here it is for pre-order! http://www.amazon.com/Art-Language-Invention-Horse-Lords-World-Building/dp/0143126466/ref=sr_1_2?ie=UTF8&qid=1430935808&sr=8-2&keywor

Here it is for pre-order! http://www.amazon.com/Art-Language-Invention-Horse-Lords-World-Building/dp/0143126466/ref=sr_1_2?ie=UTF8&qid=1430935808&sr=8-2&keywords=david+j+peterson http://www.amazon.com/Art-Language-Invention-Horse-Lords-Wor... He told me it covered the essentials of language construction as far as his methodology goes, but I think it offers some insight into the development of other major and not-so-well-known conlangs as well.