To mark books as owned, the button has two simple status where just the text changes between them. So, the button says "mark as owned" and when clicked the copy changes to "owned". It works fine but when looking at a list of books is not easy to distinguish between both and I've found myself mistakingly clicking the button because I click faster than I read.
I'd love for the owned books to be easier to spot. Maybe the button could change color when clicked or a check mark could be added inside the button when the book is marked as owned?