I basically never go into book stores, so I didn't see any of the DCC books until last weekend. They didn't feel that big when I was reading them on my e-reader.

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.

Could be that book 7 had to be printed on lighter-weight stock if the page count would have exceeded the capacity for the hard-cover binding. (They may not have anticipated that a later book would get that big when they chose the stock at the start of the series.)

I did notice some of the middle books had a shocking amount of ink smudging and that multiple times while reading Parade of Horribles I found myself thinking I must have two pages stuck together because the pages were thicker than the other books