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.
Had a twin bed similar to this once, with built in storage at the head - even a "secret" compartment under the bookshelf. Awesome Storage Ideas For Small Bedrooms : Space Saving Storage Ideas for Small Bedrooms – Better Home and Garden It looks so cosy