Mommo Design has a bunch of inspiration for girly reading nooks. These quiet corners contain fluffy pillows, rugs, cushions, usually a canopy, and of course lots of books. I think the idea is very cute and I'd love to do this for my daughter's room.
I was totally gonna do the bed-in-a-closet thing, but I LOVE the idea of this! I have a corner that is going unused and, with a little planning, could accommodate a fort/sleep space for my nephew/maybe be a reading nook for me.