The finished product looks great, but it took 7 hours to assemble.  I ordered assembly through Angi's as you suggested, however the person never showed up!  I would NEVER use Angi's again. 
The problem with assembling the bookcase was the channel on one long board was too narrow to accept the clips that were supposed to connect to the trim board.  It was not possible to install the clips with my thumbs.  When I tried a rubber mallet, they wouldn't budge.  When I tried lightly tapping with a hammer, the clips broke.   Wayfair did send replacements, but I had to wait nearly a week for them in order to assemble the bookcase. 
Be advised, there are many many many screws for the installation, and ONE HUNDRED NAILS to attach the back pieces!  So be prepared for a long afternoon.