We've shown you those Tetris shelves a couple times over the years now, but they're still really, really expensive to the point where you'd have to live inside it in lieu of an actual apartment. Here's how you can build your own on the cheap.
Instructables' guide to building your own Tetris shelves costs you only about $85 in wood ($200+ if you buy good wood), plus some more in parts. You'll need equipment like table saws and wood glue, so if you don't have that you might have to find a buddy who does. Just be careful not to line them up horizontally or else you're going to have to start all over.
Project Page [Instructables]