My copy just arrived (with the expansion) and I've played the Umordhoth and Azathoth scenarios.

I must say, while Aza is really hard (I failed) and can drag somewhat at the end, I was hooked on it's narrative and descriptions (event deck) until the very end. It's reaaaally well written IMO, capturing the subject matter with flavor and creativity. I can see why it's the recommended one for starters. It feels epic, it makes an impact. Umordhoth is much easier and simpler (and perhaps more joyful to play?) but it's narrative didn't grabbed me as much after Azzie and I felt a little disappointed in the end.

What are your favorite scenarios flavor/writing wise?