I used wood glue to glue this together.
Using that, I traced the openings for the shelves on to the back of both pieces of matboard. The matboard is white on one side (which will be the side that shows) and green on the other (inside the wall). The openings were traced on the green side.
Then I cut out the openings (the bottom three on one piece and the top one on the other piece) and dry fit them to make sure they lined up with the shelves.
The uncut section on each piece forms the back of the other shelves so I coloured those black. (This is the inside of the wall - the green side.)
The shelf sections have been painted white.
One wall was placed inside up in my gluing jig and the top and bottom plates and the outside studs were glued in place with wood glue. Once the glue had dried, the studs with the shelving crosspieces were glued in place.
Once that glue had dried, the second wall piece was glued in place white side up. I left the entire unit in the gluing jig with books stacked on it until the glue was totally dry.
I painted the end of the wall white and when the glue was dry the wall was set in place. (It's not glued at this point.)
From the bedroom side, ready for a TV.
From the landing side, ready to be loaded with books.
Straight on view:
I'm very pleased with how it turned out.
Now I have to build a proper stairwell wall behind the desk then I can install the flooring.