If you're reading this you probably own and love 7 Wonders. If you are looking to add a little more complexity and strategy with the game you'll really like the Leaders expansion.
This expansion adds, you guest it, Leaders which can be purchased before you start drafting. The Leaders add benefits, some instantaneous and others end game bonuses like giving you an extra victory point for having 3 coins on top of the normal scoring. You also get another wonder which adds some cool Leader bonuses.
The expansion integrates seamlessly with the base game and can be taught to new players without having too much more explanation. It also doesn't add too much to the quick play time of the original base game. The art on the cards are beautiful and so is the new wonder.
Definitely a must buy if you have the original and want to spice things up.