Maybe I'm just being a total noob (if so I would love to know!) but it would be super awesome if the books in your library would auto save what page you were on so you could pick it up later. I tend to jump between reading multiple books at once and I often get lost on where I was if it's been awhile.
For the meantime, I'm fairly sure you can bookmark them.
I do that for most manga I'm reading, just have a manga tab in my bookmark bar, and bookmark what page or chapter I'm up to
Would be nice if this would be an optional feature, though, in case I want to start from the beginning and not be sent to a previously read chapter instead.