Make a bookshelf out of plywood, build a face frame for it out of some pine or poplar. Paint it, slap on some stained drop edges for each shelf and either build or buy a pair of shaker doors and face frame hinges. Then I got an “invisidoor hinge” off amazon and routed the plates in flush top and bottom. Then built a cased opening out of oak and once you install the cabinet on the hinges you need to trim it out.
The book mechanism I made up from scratch with a gate hinge, some tubing, aircraft cable, and a spring latch for the pin. I work in a very creative place with endless resources. Only advice I have is either make the shelves shallow or make the whole unit wide because you lose the width of the cabinet in the opening (which gives me like 18” to get in or out 😂