Just finished assembling our bookshelf. It seems sturdy enough for its size. Assembly was straightforward. Some advice, since I saw another reviewer mention having trouble lining up the pre-drilled holes: do not fully tighten the X brace to the legs before attaching the shelves. Get everything loosely assembled, and then go back and tighten all the bolts. The levelling feet are a nice touch. 
Important note, the shelves do have a distinct greenish tint in the gray.  That is fine in my room, but just something to be aware of as you shop.