We have lots and lots of books and no empty bookshelf any more. We decided to use the staircase again but failed for long time to get a bookshelf which fits in nicely in the turning areas of the staircase.
Thus it came down to get 10 square meter of white coated wood (actually 5m x 2m) in one of my favourite stores for wood products. They turned it into slices which fit into my staircase.
To not take to much space of the turning areas the bookshelf became an elliptic shape at their front to the inside. Actually this even looks much better.
One template (Schablone) was made. All other shelfs were cut on 2 mm plus (Übermaß) at the front, then finished with milling cutter for copy purposes (Oberfräse mit Kontur-/Kopierfräser). Using that copy milling cutter in the Oberfräse leads to top results. The copy milling cutter has a ball bearing top or below the sharp part to guide along the template. So all shelfs end up the same with super precise edges.