This is the perfect place to put a pull out bed. I always look at those beds and think they're impractical because it's too hard to leave all of the open floor space needed for one but I'd happily do it for this library/reading space
This is a perfect combo of my two favorite ideas for that space under the stairs leading to the basement. A reading nook AND book storage and shelves . assuming that there is enough space for this there.
6 Pane Window for master west side wall centered & South side dining room wall & South side wall in my office & remove single window on the south side wall. Remove both windows in Ryan's office on the South side and put this 6 pane window too