I received the hardcover for Brandon Sanderson's Words of Radiance for Christmas. It's a brick that could probably be used as a base support for cathedral buttresses. I immediately went in search of the previously thickest tome in my collection, Neal Stephenson's Anathem.
I can confirm that Words of Radiance now takes the title of "(Should One Nod Off) Book Most Likely to Result in a Bedtime Reading Concussion"