Use inexpensive seat cushions in a classroom reading area. They stack up and can be tucked away much more easily than bean bag chairs or other fun chairs for kids when not in use. Comfy, fun and affordable!
If I have the space for this in my future classroom, I would love to have something like this. This establishes a quiet space that is secluded from the rest of the class. Children love making forts and tents, so I think they would find this space fun and would want to go there to read.