Death Spiral (Faith Flores Science Mystery #1) by Janie Chodosh (The Poisoned Pencil trade paperback, 1 April 2014).
Faith Flores' mother, Augustina, died the day after Faith's sixteenth birthday, and Faith went to live with her Aunt T in the suburbs. The official cause of death was listed as a heroin overdose -- Faith's mother had been an addict, after all -- but Faith refuses to believe that's what it really was. She knows her mom had been clean for a few months and was trying to stay that way, and that the dealer who turned up on that last day had set it up to look as though Auggie had shot up just before her death.
Aunt T tells Faith to stop obsessing about her mother; that the police know what they're doing and the case has been closed. But Faith's certainty that her mother didn't overdose is reinforced when she gets a note from Melinda, one of Auggie's junkie friends, telling her they need to talk about her mom's death.
Faith only has one friend at her new school, a girl called Anj, and she's made sure not to tell her anything about her background, or otherwise get too close, certain that if Anj knew everything about her they would no longer be friends. The New Boy, an odd character named Jesse, who has decided he wants to be Faith's pal, somehow manages to get her to break this rule, but when he goes along with her to visit Melinda, things get a little scary.
Faith's ingenuity at digging out the truth is marvelous, as is the loyalty and assistance of Anj and Jesse. Ms. Chodosh has created a protagonist, who, along with her friends, is smart and believable. The fact that they use the information they've learned in school, particularly in science class, to help with their investigation, is included adroitly and fit seamlessly into the narrative. I look forward to more books in this series.