Amazon – What timezone does Amazon’s “Kindle book release” follow

I had to contact Amazon's Kindle support and they reset the book's furthest location for me. This is the only way to do it at the moment.

This was just confirmed to my by an Amazon representative. However, they did mention that they added it as a feature request, so this might change in the future.

Kindle versions of purchased books appear in the Kindle Cloud Reader Library.

Alternatively, when you click on the Buy now with 1-Click button, it takes you to page that has a button "Read now in Kindle Cloud Reader" to let you read your Kindle ebook through your web browser.