It comes built as one massive piece and you just have to screw on the top 2 posts and levels. Easy. But you cant take it apart. I had planned on moving some pieces around to make it work better for my senior cat, which isnt possible. 
It really is good quality. Its heavy and sturdy due to the real wood, and the carpet is thick and soft. The u shaped platforms could use some better support, the the cats seem okay with it so far.