Trade-skill Book: Glorious Gnomish Cultural Tinkering, is missing from the cultural historian in POK. As a point of data, I recently changed the race of my rogue from Barbarian to Gnome so that he can learn to tinker.
That was a good point. I leveled up to 300 and it was still not there. Perhaps I need to do the cultural quests but I can see all the other Cultural TS Books. At best, its inconsistent.