That's another great thing about this design: Expandability. If (when) I need more space I can just buy another shelving unit and add it to the top.
I'm not a carpenter and I was able to put it together solidly and without a lot of trouble or tools. I'm sure it's a little more substantial than the ones you could buy premade, but there's really no concern about it falling apart, and I spent 1/3 what I would for the same space from an online store... and I got it pretty much immediately.