The news section of Bulbapedia just posted an article about it- the book will feature 192 pages of illustrations from the TCG! These will include illustrations from the very beginning. I'm suuuper excited for this as an artist and a pokemon fan! TCG artwork has greatly inspired me over the years. I really hope this gets released outside of Japan!
And for you TCG collectors, it also comes with 2 promotional cards:
Check out the original article here: http://bulbanews.bulbagarden.net/wiki/Illustration_Collection_TCG_artbook_being_released_Dec._13