Had to go back and look at the photos again. And place the round table between the chairs. What is under the carpet? Something different on the floor would make it cozier. Tidy up the shelves - donate anything that is not useful or meaningful including books. It’s a great spot for photographs, mementos from trips, etc.

Looks like we've got a view right there and I'd definitely try to make use of it. You could also look into contrasting paint colors instead of plain white. That coupled with a set of nice lounge chairs and a small office table and chair, I think we have quite a cosy home office. I'd consider bringing in a small bookshelf to replace the dresser and cupboard we have due to space. Some lamps, fan and flowers work well too. Check me out fiverr.com/ndegwagakumu

The large bookcases and file cabinets are beautiful, but they are overwhelming the small room and limiting your options. Would it be possible to repurpose them somewhere else in the house? Yes, you need need some bookcases for a reading room, but perhaps shorter ones that would fit under the two windows. Aside from that, you need two comfortable chairs, at least one floor lamp, and a small coffee or end table between the chairs, at a minimum.

Does the top come off the bookcase? If so, relocate one half of it elsewhere in the house and keep the other in the room at the far end to use as a bookcase or a console. Then add a couple chairs facing the windows or each other with round table in the middle.

INK+IVY Rocket Lounge · More Info

How many people do you want to seat in the room?

Remove all current furniture, there is nothing more modern about it. Keeping with the Craftsmen style high windows, bookselves under the ledge.
Long wall opposite the full windows would be a great place for comfy reading chairs with table and lamp in between. Add a hassock to be used for puting feet up or additional seating if moved underneath the full windows.
Fllor- expose wood, maybe?
Windows, Roman Shades if privacy, or sheer panel.