So, two things with the gifts. First of all, as mentioned by another, I can't access the last couple gifts because they don't fit in the UI when you have everything purchased.
Secondly, despite owning 5 of the chocolates, when I gave them as a gift once, they all vanished from my inventory. This helped me now be able to access my culture gifts, whish I suppose is an added benefit, but I definitely think it's also a bug. :P
Edit: Now that I check my inventory again, the History Books don't seem to have been consumed. I definitely gave away two of them, but I still have all five in my inventory. :/
So, yeah, maybe double check the chocolates and the history books?