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.
IKEA Bedroom Design: Drape sheer fabric panels from curtain rod mounted on ceiling. Scaled back princess bed! Beautiful as long as you don't forget to clean the dust, cobwebs and other stuff before your allergies kick your butt.
Simple built-in to create a mudroom and/or storage anywhere from an entry, to kids room or in a laundry room by adding shelves or a deeper bench for sitting. Put drawers under bench or have the seat lift up to store things.