This looks like a great shelf! The followings reasons I’m giving it four star instead of a five
1. Very light weight. Has its plus but feels kind of cheap. Possibly, easy to topple over. Need to anchor it to wall especially if you have pets that like to jump on shelves. 
2. There were boards that the instructions said needed to be screwed but there was no pre-drilled holes in some locations. Which isn’t a big deal if you’re used to building furniture but it can make it much easier to split wooddamage the shelf with a pre-drilled guide for the holes. 
3. It is a bit difficult to build by one person. Ideally need two people but it’s not impossible to build by 1 person. If you’re careful with putting in the screws to build the corners of the bottom cabinet, then everything else is easy.