Sorry! Been on vacation and before that I was running around like a chicken with its head cut off trying to get things done.
The most important part of making a factory bookshelf look custom is by framing. Make sure you place and anchor the bookshelves evenly, then measure, then re-measure, then measure again... for good measure. You want the boards to overlap by about 1/4" (lesson learned!) because you never know if there might be the ever slightest sway of a bookshelf on uneven flooring (again lesson learned!).
After you have your measurements bribe a friend with a truck or SUV for a day of fun at Lowe's or Home Depot. You want a 3/4" board and I chose poplar because it has less dark veining and will require fewer coats. One board should cover everything. They'll do the cuts for you there though I found buying an $80 circular saw came in very handy for getting the length of the boards cut perfectly. After you have that you can start adhering them to the bookshelves. Apply a line of wood glue (seen right) and nail or screw the board on. I chose flathead screws but that required a lot of pre-drilling. I would almost recommend a nail gun for finer tuning.
After those initial boards were put on it was time for the top pieces. I anchored a 2" X 4" across the top and (with the help of a friend to hold it) screwed in the top poplar boards. After that I nailed the crown moulding and trim (annoying little buggers and hard as plastic), as well as the baseboards. And then, voila! You have a framed book case. Next up- finishing.