As others said, it was covers out, which in my opinion only had the downside of having limited shelf space.
I've always found the physical similarity of Amazon's own retail store efforts to Waterstone's curious, as Amazon actually tried a partnership with Waterstones to sell Kindles and such years before opening their first stores back in 2012... First Amazon book store with remarkably similar design and layout to a Waterstones followed in 2015. As a UK expat living in the US my first thoughts on entering an Amazon Book store here was just how much it was like Waterstones.
Could just be coincidence!
> https://www.independent.co.uk/news/business/news/waterstones...
> https://www.theverge.com/2015/11/2/9661556/amazon-books-firs...
It was pretty weird.