The Components
The Catan Event Cards comes with 43 cards in a small baggie. The cards are half-sized, printed on attractive, glossy stock.
36 of the cards depict the standard results of rolling two dice, from 2 to 12. Each card also has a small slice of artwork, all of which are attractive drawings by Tanja Donner. The 37th card goes with the dice cards, and is a "New Year".
The remaining 6 cards are score cards for the six player colors. Each one runs from 0-9, with additional spaces maked "10+" and "20+" (though why you'd ever need a 20+ in Catan I can't imagine). These cards are simple, but very helpful. I've always been frustrated by having to constantly recount points in Catan, and this does away with the issue.
Overall, the cards in the Catan Event Cards are all good quality, attractive, and easy to use. I've thus given then a "4" out of "5" for Style.
The Gameplay
The Catan Event Cards introduce a deck of 36 cards which replace the normal die rolls in The Settlers of Catan. At the start of the game they're shuffled, then the "New Year" card is put five from the bottom of the deck.
The cards match the bell curve distribution for two six-sided dice, meaning there's one "2", two "3"s, three "4"s, etc. Because the "New Year" card--which causes a reshuffle--is put five cards from the bottom, only 31 of the 36 cards will appear each time, introducing some randomness.
Besides showing a die roll, just more than a third of the cards also have a special event. These include: bonuses for the players with largest army, longest road, and most ports; a few results where cities don't produce double; a penalty requiring the lead player to give away some resources; and a few other items. They're generally colorful without shaking up the game too much.
Besides the changes in die rolls and the events, using the Catan Event Cards doesn't change the game of The Settlers of Catan.
Relationships to Other Games
These cards are a supplement to The Settlers of Catan. They can be used with any of the expansions, including Seafarers and Cities & Knights.
This is one of several expansions that was released in Germany as part of the Atlantis supplement. The Great River was another.
The Game Design
The biggest change resulting from the Catan Event Cards is that they make the "random" rolls of standard Catan into "arbitrary" card draws. These means that there is less variance: you have a lot more surety that the random selection will be somewhat nearer to the average.
I was a bit surprised to see that this has a real effect on the game. You could be vaguely aware of what had come up already, and really plan for futures. This card-counting ability makes Catan slightly more strategic and rewards more thoughtful play, which is all around good.
The actual events added color, but didn't do a lot more. There were some things that punished the lead player, but there were also things likely to reward him, and so I think it balanced out. One of the events, the "Earthquake", irritated me because it broke roads two or three times during the game, but the rest I found interesting.
Overall the Catan Events Cards felt like they notably improved The Settlers of Catan and are thus recommended for any serious game players. I've given them a "4" out of "5" for Substance.
Conclusion
Although based on a simple idea--replacing die rolls with card draws--the Catan Event Cards actually add a lot to a game of The Settlers of Catan by making it more thoughtful and strategic.

