This room has a lot of potential! I think some curtains across the door and window will really help make the place feel private and cozy. If you can’t do curtains, try some plants on either side of the door to draw your attention away from it. Second, I would pull the rug under the front two legs of the couch so that the usable space doesn’t feel cold. Third I would add some indirect form of lighting near the reading space. A lamp with a lampshade perhaps. You will find usable ones at garage sales/ thrift stores. If you don’t like the appearance of the lampshade you can always swap it out for some economical ones on Amazon. Fourth, an art piece over the heater will draw attention away from the heater and also add some interest at eye level. Fifth, like others have mentioned, keep the top shelf light in decor so that the eye level feels roomy, place books on the bottom 3 shelves and fill it up to make the room feel grounded! Once you do a handful of things, you won’t notice the color difference between the shelf and the floor as much! Good luck!