Super-sturdy, well-designed and simply beautiful.  We absolutely love this bookcase!  Assembly took us a little longer than projected; the shelf arrived in three, well-packaged boxes and we took the time to inspect and separate all pieces.  The instructions were a little confusing at first, but then we realized that the booklet contained directions for both, the four AND five units with specifically saying so.  Once we realized that, the instructions were simple to follow.  Assembly is very similar to most IKEA units.  All parts fit perfectly.