if you're used to western rpgs based on DnD archetypes (i.e. most of them) you will be confused at first because it is based instead on the dark eye and uses some different skills and ideas, but you will figure it out. no worries!
das schwarze auge (the dark eye) is so much so much better than d&d imo. no wonder d&d is kind of unpopular here in the german speaking world.
Why's it better?
the rules are less combat-centric, there's a broader range of skills for different stuff and character generation is more detailed. i also like that it's not just a "system" but comes with a fleshed-out setting (that isn't just a generic tolkien ripoff) out of the box. in short it feels like a more complete roleplaying experience to me than d&d.
also i grew up with it

this.
(disclaimer: I never played DnD PnP, just heard of it...)
DSA/Aventurien is a very "realistic"/authentic approach for a fantasy world.
on the downside: with more rules and content you might feel limited in your fantasy. there also might occur discussions about history, gods, appropriate behavior of elves etc. because so much is written down, some guys always know better...
of course good players know to handle this.
just imagine an rpg made by slightly pedantic Germans.
Amusing American Amazon review:
This game system is very math-heavy. If you like juggling lots of numbers while trying to run your character, you'll love it. Otherwise, you'll quickly learn to despise the system, since the math constantly interrupts roleplaying. It's obvious that sales of the game, between 2003 and 2011 (now) have been horrible at best, since the company that translated the game for use over here in the U.S. has long since gone out of business. The only reason I bought the book is to act as a manual of sorts for the computer game Drakensang, which I'm told is highly underrated. Of course, the company that made the computer game also went out of business.
The ruleset version before the one he reviewed is even more complex. And he only reviews the basic ruleset for beginners

. AFAIK currently there are 3 basic rulebooks: one for magic, one for combat and one for character management. Of course there are additional content books with additional rules. Selling rule books is an important monetization strategy for DSA ^^.