SOME of Dewey Larson's books are available for purchase through Amazon.com. The reason that all of them are not there is because they have never been allocated ISBN numbers, and Amazon's service to add your own products (that do not have ISBNs) is too costly for ISUS at this time.
IF YOU ORDER FROM AMAZON, it goes to the SAME place as placing an order directly through this site--namely, me. You can save money by ordering direct through the ISUS Store--Amazon prices are higher than here because of the fees they charge (which have become substantial for small orders), plus they charge shipping for EACH book. The ISUS store charges shipping and handling for the total order, based on the USPS quoting system.
There is NO DIFFERENCE in service... I still pack and ship the books, usually by the next business day.
I have set up discount plans for resellers, distributors and large purchases. Contact isus-store for information.