Do I need to play The Dark Eye: Chains of Satinav before playing Memoria?

Is Memoria a direct sequel to Chains of Satinav, or is it just a sequel "in spirit?"

Do I need to play Chains of Satinav to understand the story of Memoria?
Will playing Memoria first ruin the storyline of Chains of Satinav?

Now that I've beaten both games, I feel comfortable in answering this.

Memoria is the sequel to Chains of Satinav. It is technically a continuation of the first game, with most of the same characters. However, the story itself is almost completely unrelated, and the events of the first game are only mentioned in passing.

Thus, it's completely possible to play Memoria without playing Chains of Satinav first. However, I wouldn't recommend it, because the ending to Chains of Satinav would be ruined in the first few minutes of Memoria.