The pages feel thinner and you can see the text on the other side more as well. Book 6 is a 10th printing and book 7 is a 5th printing. Doesn’t say years, so I wonder if they switched to thinner or back to thicker?
Take a look at book 7 of DCC. That's bone. And the lettering is something called Silian Rail. Impressive. Very nice. Let's see book 6. Look at that subtle off-white coloring; the tasteful thickness of it… Oh my God, it even has a watermark.