Got my copy of the core book book just in time for Christmas, and it's a beaut!
There's so much to love in this. The layout is set up so that each page or two-page spread is one topic or sub-topic. The art is very reminiscent of early D&D art, in the best possible way. The random tables are bursting from the seams, and could be ported into any game. The sections of the book have black boxes on the outer edge of the pages, so that you can see the different sections when when the book is closed.
It's just kind of a masterpiece and I love it.