Future Horizons - This organization publishes autism literature and puts on autism workshops throughout America and other countries. The Morning News - This quarterly newsletter informally shares practical information among parents and professionals working on the behalf of people with autism. Articles address various concerns and share ideas which amplify social stories and related techniques and materials. See webbsite for sample issue. It goes without saying the most cost-effective way to obtain these books is through the library and borrowing from other parents and professionals.
Some books are mainstream and can be found in national bookstore chains.
For the ones that aren't, most of them can be ordered from ARI, Future Horizons and some chapters of the Autism Society of America.