For reasons that presumably make sense to them, Ubisoft have the English forum for the Anno series on the German forums ANNO - English speaking forums, and it's only called Dawn of Discovery in the US, everywhere else in the world, it's called Anno.
It's a good game, but if you're unsure, maybe you should try the demo first.
I personally find the settlers a very good game, but anyway I am posting to correct you on something. Anno is not made by the same people as Settlers. Both are published by Ubisoft but they are developed by different studios.
I have played both games and run fansites for both (shameful self-advertising - see links in signature)
Both games are similar in many respects where you have to build up your settlement, find raw materials and engage in combat. Here is a breakdown of the differences that I think make both games unique:
Settlers 7: You play on 1 big island with other players battling for supremacy.
The victory points system makes it a challenge to find different ways to play.
You can see the progress of your building work and can take pride over the way you set up your town.
The quest areas give you a great challenge - even if not useful, just to complete.
ANNO 1404: The whole playable area is split up into islands which you navigate via ship.
When you build your city, the buildings are erected instantly so there is no timke to wait - you are only held back if you have a lack of raw goods.
The multiple quests are a good addition and can be ignored without causing detrimental effects to your game.
The amount and style of buildings and city ornamanets you can build is very impressive.
The battle system is lengthy but great to watch and control - gives great satisfaction when you finally drive another player off the map.
In summary, I think, if you like The Settlers then you will like ANNO 1404 and vice versa. Each have their own style and gameplay which means you dont play one and not bother with the other cause you think it could be a clone.
As BTOG46 mentioned - try the demo first - it doesnt give you a complete overview but will give enough info to tell if you will find it interesting