The shelves themselves are really strong and sturdy, especially for the price. The building instructions are great and literally come with a blueprint (to scale) to help build and advise where to drill. 
Now the thing that turns these shelves from a 5 to 3 are the hinges and screws! The hinges so visible and completely ruin the look and vibe. The screws arent adequate to hold up the weight of the shelves (these arent your average mdf shelves) so we used stronger wall plugs and better screws.
We got it on sale so all in all, cant complain too much as it does look great (minus the hinges).