I'd love to be able to add a comment when adding a book to my TBR. I currently try to use tags to keep track of where a recommendation came from, but it'd be great to be able to record why I thought I'd like it, as it would influence when I wanted to pick it up. For example, if a book is described as a readalike to a book I loved, or about a particular topic, it would be great to be able to record that information.