On day 1, I bought tier 3 - I normally buy tier 6. I reluctantly paid for tier 4 on day 7 because my guild was just shy of clearing the reward for the books. Still, they missed out on 850 gems that I would have easily spent before. It will be interesting to see how the next one is presented to us.
I’m assuming purple wargare was to incent additional gem spending because they know people really want purple books.