Planetfall focuses on Renata (Ren) Ghali, a founding member of the colony that has established itself on an alien world at the base of what the colony members call "God's City." There are religious overtones there, but I wouldn't call all of the colony members fanatics, despite having followed their prophet Suh-Mi to this planet to find this city. In Ren's case, she was her best friend.
The colony's ordered existence is disrupted by the arrival of the sole survivor from a group that had been believed lost and and presumed dead when the colony members originally made planetfall. This newcomer will rip open old wounds and lead us to uncover secrets that have lain buried for twenty years.
This book wasn't heavy on the SF elements, although, you know, alien world. It's more about uncovering the mysteries from the colonists' planetfall and exploring Ren's perspective and capacity for compartmentalisation. Let's put it this way: she's not well. I thought it was well done and found it to be very engaging.