Step 1: Determine the size of the opening
I wanted a built in look, with 3 sections. this allowed me to have the certain bookcase be my "door"
My approach was to find a way to have the bookcases appear to be static, yet roll open when needed.
As you can see in the photo, I have an arch to deal with as well as an opening of about 59"
I decided to get 2 CD towers from IKEA (Billy model) and one 30" bookcase from Walmart.