This error can occur on the login screen when you enter your username and select "Continue".

Unfortunately there are many causes so it is difficult to diagnose. But one easy issue to check is this.

Sometimes if you visit eBooks.com (especially on Mobile), and you are already signed in, if you select the Sign In link before the website can update to recognise that you are already signed in, then when you enter your username and select Continue you will receive the error.

The developers are going to fix this issue, but for the meantime, please try going back in your browser to the eBooks.com homepage and wait for 5 seconds to see if the 'Sign In' link disappears and the website shows you as signed in. If it does then you can simply continue using the website. If it doesn't change, then please try signing in again.

If you still receive the error, please take a screenshot (with your username showing in the Username field) that shows the error message and the URL in the address bar and send it to us by completing our support form to submit a ticket to our customer support.