Little Fires Everywhere by Celeste Ng

In 1998, the Richardson home catches fire. Arson is suspected, as there were multiple small fires.
The previous year, 1997, Elena Richardson rents her rental home across town to Mia Warren, an artist, and her teenage daughter, Pearl. Elena's younger son, Moody, who is Pearl's age, develops a crush on Pearl and becomes friends with her. Pearl meets his siblings Lexie, Trip, and Izzy. Pearl, who is used to a transient lifestyle in which her mother scrapes together money, is charmed by the Richardsons and their established home. 

Mia works part-time at a Chinese restaurant and sells photographs through a dealer in New York. She becomes concerned about Pearl's idealization of the Richardsons. When Elena condescendingly offers her a job doing housekeeping for her family, she agrees only to keep an eye on Pearl. She meets Izzy, the black sheep of the family, and the two become close.

The Richardsons are invited to the birthday party of Mirabelle McCullough, the adopted daughter of Elena's friend. Mia realizes that the child is May Ling Chow, the daughter of Bebe Chow, Mia's co-worker at the restaurant, who gave up her child in the middle of a postpartum episode and economic hardship. Bebe has been looking for her child for over a year.  The scandal results in Bebe getting visitation rights and help from a lawyer pro bono.

Elena discovers that Bebe learned of her child's whereabouts through Mia. Angry on behalf of her friend, she investigates Mia's past. She tracks down Mia's parents and learns that Pearl was conceived by Mia for a wealthy New York couple who were unable to have children of their own. Mia could not face the idea of giving up her child. She told the couple that she miscarried and ran away with Pearl; Mia's parents hadn't heard from her since.
Lexie gets pregnant and asks Pearl to come with her to get an abortion. Afraid of being discovered, Lexie uses Pearl's name at the clinic. 

Bebe Chow loses her case and Mia comforts her. Elena tells Mia she knows about Pearl and that she must move out. Pearl is reluctant to go, but Mia explains about her biological father and she accepts. Izzy realizes that Moody, Lexie, and Trip have all used Pearl in their own way and becomes angry at them. Choosing a moment when they are all out of the house, she starts small fires on everyone's beds, not realizing that her mother is still in the house. Elena manages to escape the fire unharmed. After the fire, the Richardsons go to the rental home, now vacated by the Warrens, where they find that Mia has left them with photographs that have personal significance to each of them.