Book of Bushido 0 Spells

[Luke Carjacker]

I was wondering if anyone could tell me about how this happens. I found a few Bushido books lying around Luna bank with zero spells in them. I know that, for a time, spells could be removed from Chivalry books and that those books with zero spells are sometimes offered as rares. Never heard anything how this could be done to Bushido books. Anyone know where these come from, and if they are unusual or rare?

BTW, if you try to cast a spell while carrying one of these, it says "You do not have that spell".

Thanks,