The Binding of Isaac is not a game that really requires any addition. Its rogue-like qualities and massive collection of power ups, tarot cards, and abilities ensures a completely random, unique experience every time that you play. That, coupled with a fairly conclusive ending to the game's thin story, made it a prime candidate for being a one-shot title.
Wrath of the Lamb is not your typical DLC. It doesn't add on multiplayer, or any real additional story. What it does instead is add in 50% more content to the game proper, folding the new assets in to the original game in a seamless fashion, raising the already massive quantity of variables to dizzying numbers. While an infinite number of unique games generated may not be mathematically possible, Wrath of the Lamb comes pretty damn close.
The bulk of the new additions come in the form of power ups, which give Isaac an arsenal of new abilities with which to dispatch the monstrosities that lurk beneath his mother's house. There are literally dozens of them, including a set of new items called "trinkets" which introduce a series of new, passive abilities that aid Isaac in new in interesting ways, such as raising the odds of him finding higher-end items or enhancing the destructive ability of Isaac's tears. These trinkets add an interesting wrinkle to an already simple, yet effective game mechanic, and are a welcome enhancement.
The other major addition comes from a horde of new monsters and enhancement to the current bestiary. A clutter of spider-like enemies are the most notable and omnipresent, moving erratically and providing a firm challenge while the Widow, an arachnid beast made from an inverted human head (shades of The Thing) that is positively brutal in its difficulty level. A handful of other new bosses round out the experience, each providing a unique challenge, even the ones that are little more than variations on previous beasts.
While Wrath of the Lamb is not your typical DLC, The Binding of Isaac is not your typical game. The promise of 50% more content blended into a game already bursting at the seams with variety is a welcome one, and the tiny price tag--$2.99 as of this writing—is simply too good to pass up.
The Binding of Isaac: Wrath of the Lamb is available on Steam for $2.99.