I put this book on my get-at-library list thanks to its nomination for a "Best Novel" Edgar award. And (in April) it won! So: good for the author, Deepa Anappara.
The novel's setting is a poverty-wracked slum tacked onto an unnamed Indian city. The "Purple Line" in the title is the commuter train that runs under the slum. And the Djinn Patrol? Well…
The narrator (for most of the book) is Jai, a nine-year-old boy. He's very observant and insightful for his age. And he takes for granted a life that we Americans would find horrific: grinding poverty, pittance wages for shitty jobs, communal bathrooms, open garbage dumps, choking air pollution, lousy schools, Hindu/Muslim bigotry, corrupt and lazy cops. And the ever-present threat that your entire community's housing could be wiped out in minutes without warning if the powers-that-be decided to bring out the bulldozers.
But things get worse, because kids start going missing from the slum. Did I mention the corrupt and lazy cops? Yeah: they're willing to take hefty bribes from distraught parents. In exchange for not doing anything.
But plucky Jai does watch TV, enraptured by crime shows. Inspired by the fictional detectives, he decides to investigate the disappearances on his own. He teams up with his school friends: Pari (a girl who's significantly smarter) and Faiz (a Muslim boy). Their efforts are largely unappreciated, but their story illuminates much of the city's social ecology. And Jai entertains the idea that the missing kids might have been kidnapped by an evil djinn; hence the "Djinn Patrol" of the title.
It's very well-written, and (surprisingly) it's not without humor amidst all the bleakness. I didn't care for the ending. No spoilers, and your mileage my vary if your tastes in crime fiction run a certain way, but… no, I didn't care for the ending at all.