I do not believe you can find a more complete book on the subject of American ragtime than <That American Rag> by David A. Jasen and Gene Jones (Schirmer Books, 2000). It tells in some 307 pages of text and another 100 or so of lists and charts "the Story of Ragtime from Coast to Coast" in great detail, far too great for quick reading. Indeed, I am going to use this tome as a reference book in the future as a source of information for my articles and talks, with due acknowledgment of course.
Starting with the seeding and growth of rag in the fertile soil of Missouri, this book traces the development of the form through the sections of our country, ending up with New York City. The material is further organized by composer and publishing house, so it is easy to locate any particular composer by using the table of contents rather than the index. But again, I suggest you assimilate all this in small doses.
While I am giving this wonderful history a top rating, I must voice a personal observation concerning what I think is a curious omission. There is much mention about this and that rag being a masterpiece or at least immensely popular or pioneering; but I fail to locate a single explanation of WHY the music was so important or different. Perhaps the authors preferred to avoid musicology, but I still consider this a real lack in an otherwise excellent work.