That's a neat idea. I would probably need a lot of these because I own a lot of books. Great DIY idea for bookshelves.
Glass railings and open partition in a staircase in a mews house London& Knightsbridge neighborhood designed by Elips Design
Mountain Hill Cabin Norwegian architects Fantastic Norway have designed a mountain lodge with a sloping roof that you can ski over.
stairs/balcony to upper floor
Jungle Lifestyle In A Panchoran Retreat In Bali. Not a tree house, but it is awesome!