Adjustable Bookshelf for Angled Walls

Since angled walls/roofs are hard to make shelving systems for, I have made a bookshelf to utilize this mostly lost space.
You can adjust the bookshelf to every angle, by adapting the bolts en setting the angle right. 
If you want to, you can also put it on a regular wall, wherever you want, or on a flat surface. Of course you don't have to use it for books, you can put any stuff you want in it.
As we had to move the bookcase several times to take pictures, I didn't secure it to the wall, because that would make too many holes in my walls... Therefore you can see my hand on most of the pictures.
The system is not expensive, I only had to buy wood and bolts/screws.
The whole built took just a few hours. It is extremely convenient!

The materials I used:
-Long pieces of wood 
-8 screw bars (30 cm each)
-16 irons nuts

The tools I used:
-A drill
-A saw
-Some sand paper to finish the edges

The basic steps:
-Cutting the wooden pieces to the right size
-Drilling the holes for the screw bar 
-Assembling and attaching the wooden pieces to the screw bars
-Tightening the bolts
-Finishing the corners with sand paper