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.
DIY floating shelves for a small space - master bath idea above toilet
slanted ceiling bedroom 15 Charismatic Sloped Ceiling Bedrooms For the Home
Under stair closets - doors on the side are so much more accessible! For my basement stairs!
Under stairs reading nook - apparently I need a house with lots of staircases for all these neat ideas