Good Morning, I have purchased a 'book/iPad' holder like the one you shared.
https://smile.amazon.com/Bean-Lazy-E...tablet+cushion It's wonderful to use, especially with my 12" iPad. It is filled with those small styrofoam pellets and they are enclosed in a separate bag so you can pull them out to wash the outer bag. I've not tried to read a book using the beanbag. The only problem I could see is whether or not the pages would stay open. The bag is very light weight so it's no problem to hold.