The book shelf part has hinges that are pre-attached to the back and sides.  You are supposed to open the sides, 90 degrees, to allow the shelfs to be placed in-between the two sides and back.  Upon opening the sides, they only opened about 60 degrees instead of the 90 degrees they were supposed to open to.  When a little pressure was applied to the side, it split the particleboard without ever getting close to the 90 degree mark.