This is the perfect place to put a pull out bed! I always look at those beds and thing they're impractical because it's too hard to leave all of the open floorspace needed for one but I'd happily do it for this library/reading space.
guest room - How absolutely handy! This would really optimize spare space and families are always more inclined to sleep with their small kids in the room with them!...of course there would be railing on the top. More