This expansion adds more cards and a couple of new mechanics. I've played the base game to the point where it is starting to feel a little similar each time, and thus Martial Law was a very welcome addition. I particularly like the way this expansion focuses on Minions and gives them a greater role to play, including giving them many new abilities.
Do you like Nightfall? Get this. Doubles your draft pool with all new clan vampires and cards to help counter the various werewolves and bloodsuckers that are out to get you. One of the best and most combative deckbuilders out there.