When you post a link to a Bloom book (either the book’s record or the read online version) the image that Facebook uses is just the site image, not anything from the book. I have no idea what FB is looking for, but I wonder if there’s a way that site that use a graphic to represent a link would be able to pick up the book’s thumbnail or cover image.
Yes, this would be a nice feature to add.
The problem is that Facebook doesn’t work with sites, like bloomlibrary, which run in your browser (no server). There are a couple ways we could build a system to create, for each book, a special html file for sharing with FB. It’s fairly involved… maybe a week’s work.