An invalid ASIN message is popping up regularly for unopened e-books that were either sideloaded via USB or delivered to the reader with the Kindle email system. There is a temporary workaround, but Amazon is aware of the problem and is hopefully working on a solution. The full error message that is popping up says “Invalid ASIN — Sorry, the selected ASIN is not valid for digital purchase on Kindle. Please continue shopping in the Kindle Store.” This Invalid ASIN message has started appearing in the last week. An Amazon Kindle representative told Good e-Reader, “Our technical team is aware of the issue and they’re working on a resolution.”There is a workaround right now to stop the invalid ASIN redirection loop.