In order to fit all the pieces into a short box, they are cut into little sections.  Unlike a standard bookcase, for example, the back is in six pieces instead of one big sheet that would keep everything stable.  You have to screw in 24 tiny angle braces to stiffen it up.  Same for the two side panels -- they are cut in half, requiring more screwing to rejoin them and stiffness suffers as a result.  I counted almost 60 screws that had to be driven to assemble it, all because they wanted to save on shipping by using a short box.  Count on a full afternoon of fun!