Super unstable, which could be solved by attaching the shelf to the wall. But I wouldn't trust it with too many books on it. 
The main complaint is after assembling it upside down (as instructed), when flipping it straight, parts starts to fall off, which is an extremely unpleasant experience. Smashed my floor, caused permanent damage over itself, screws were tilted, it's a mess. 

The material also looks cheap. But that goes with the low price, I don't have a particularly strong complaint for this issue.