Good excuse to cut stuff!
I cut it down the middle and wound up with two 8" deep shelves that fit perfect.
Note: the backs of the new shelves look very unfinished, if that bothers you don't cut it! Up against a wall you cannot tell.
I used the shop and great table saw at http://makerplace.com/ to do all work.
Step 1: Mark Centers
Step 2: Cut It
Step 3: Add Shelf Support
The backs of the shelves now need some support, I added finishing nails through the uprights into the shelves.
Use long screws to attach top/bottom portions.