"The Calling" is the first book in a series called "Finding Humanity".

Well written, with engaging characters and a good pace, we follow the experiences of two groups of people on Earth, one on the surface, one underground.

The ones underground are determined to find other havens where people live, but that's easier said than done. Expeditions to the frozen surface require a lot of preparation, and resources are limited.

Be ready for misunderstanding, rigid minds and insights of many kinds.