We lucked out, our closet was the PERFECT size for this. 
The instructions are pretty straight forward aside from a few things that can throw you off a little bit. 
For example, it recommends hanging the rails up starting at like 19” from the corners. This only works if you’ve got a larger closet space and don’t want it starting at a corner. 
If you you are going to have it flush against a corner make sure the rails go all the way to the corner. 
I wouldn’t say it’s “hard” to put together but it’s definitely something you want to take your time with when putting up. 
All in all we are very satisfied with the closet !