Also, could anyone out there please share with me the reasoning behind this insanity?
This "insanity", as you call it, was the only way that we could see to protect the book from being illegally distributed, or "pirated". If you can suggest another method that Shopatron can handle, I'd be pleased to hear it.
The password is your Shopatron password. That's the same one that you created in order to login to Shopatron to purchase the book. If you've lost the password, simply go to the Shopatron web page where you would normally log in and click on the "Forgot your password? Click here." link under the entry for the password.
Follow the process to get a temporary password that you can then change to a new, real password. Then, re-downlaod your eBooks (free of charge) and use the new password to open them. Delete the older copies since you cannot open them any more without knowing your original password.
By the way, if you open the book frequently, on a computer or mobile device, you could just leave it open after you're done using it. That way, the book will stay open between sessions, and the password will not be required the next time that you access the book.