GW has put a preview of the new 40k expansion online.

"The new 80-page Cities of Death expansion lets you expand Warhammer 40,000 to fit the urban combat environment in a way that gives you equal doses of gritty realism and playability. This book explains in-depth how to play your games in the bitterest of battlegrounds, including how to categorise terrain, how to play on and through structures, and how to organise a city battle."