For me it entirely depends on how thick the book is. It's easier for me to read doorstoppers if they're hardcover - I can just lay them down and not have to hold up a 1000 page book for however long. But for shorter books it's easier to read them in paperback form.

Also I don't think reading and decorating have to be mutually exclusive. I use my books as decoration when I'm not reading them. So I have to redecorate from time to time as books come in and out.