I only had the Japanese Armor/Weapons books to test (The Art of Japenese Armormaking and The Swords of the Samurai), and it seems that none of them contain any recipes, despite my character having the required skills to learn them. Before, I remember the books working as normal, but now it seems they don’t!
I am not sure if the other weapon/armor books are missing recipes as well. This is while I was playing on the Experimental Build as of Sep 19.