How puzzeling..

I was given this puzzle recently. The object is to take the pieces apart, and put them back together again. Simple? Well it turns out the pieces only fit together in one direction (the slots are angled), and each piece fits into any other, some fit better than others. The first thing I think when playing with these puzzles is about their physical nature. Can I break it if I'm not careful? What if this was incorrectly manufactured and doesn't actually work? That last one was on my mind the whole time while solving it, and proved to be my weakness. While some fit better than others, it is intentional rather than a mistake.

There seems to be a major, and a minor difficulty in this puzzle. The major is that the slots only fit one direction. This is a base of the puzzle - how do they fit together? In which order?
This by itself would lead to a good puzzle, but then there's the extra layer added - the minor difficulty of having some fit better than others. While playing with it, it is hard to tell if it is just a manufacturing problem.
But having solved it, I realise it is not. It creates a solution that can only be solved with the pieces in a certain order - made even more difficult in that none of the pieces are uniquely marked (save for the copy-write mark on one)

It is a good puzzle, the major difficulty is a good one, while the minor is a basic way to make it harder - I would say that the minor difficulty seems like a cheap shot, except that it creates all sorts of solving problems that make the puzzle more intriguing. Why does it fit this way? Is it a trick? Did I miss something? It's magic!
I must also add the physicality of it is beautiful, it feels like knocklebones - and makes the same sound when it pieces. It's just nice to hold even - giving it use even after it has been solved.