The RPG resource review has mentioned almost everything I have to say about this module.

I'd definitely recommend using "The Doom from Below" in conjunction with "Murder of Crows":
MoC as a kind of prequel to the exploration in TDfB. They complement each other very well: MoC has enough interaction to smooth over the lack of social encounters in TDfB. (Which is understandable, considering the nature of the module.)

The finale is awesome and really something different. Highly recommended to kick off a new CoC campaign, especially in conjunction with MoC.