Scroll down towards the bottom of the page at the link to find the free downloadable plans to build a built-in bookcase.
It needed to be no more than 10 3/4 inches deep and could not be more than 42 inches wide to fit perfectly in this space. And that is precisely what this is, and plan for a Faux Mud Room Locker Cabinet with a narrow profile!
On permanent display: mahogany, solid biscuit joints and a whole lot of class. Build this built-in unit using these free plans.
With the right plans, materials, and equipment, you can construct a Built-in Wall Bookshelf as shown here.