This is a hit with ladies in my life. (Wife, mom, mom-in-law, sister, sister-in-laws). I simply take a hollow-core interior door (32″ and 36″ are the best) and cut it just to the side of center and bring them together to form 90 degree angle. I support each shelf and the top and bottoms with strips of 1/2″ quarter round. The shelves and top and bottom are from sheets of 1/4″ plywood. I use 3 5/8″ base board for the bottom molding and 3 1/4″ chair railing for the top molding. Two or three coats of paint, install a door knob and you’ve got a door bookshelf.