'Gone Girl' Author's New Film Adaptation Is Out — And It's Just As Insanely F–ked Up

'Dark Places' isn't afraid to show humanity at its worst.

As of yesterday (August 7), the film adaptation of Gillian Flynn's 2009 novel "Dark Places" is available to see in limited release theaters and On Demand. It was based on her second book, the one she published three years before the world ever heard of Nick and Amy Dunne from "Gone Girl."

For those of you who haven't read the book, it's about Libby Day (Charlize Theron in the film), a young girl who is the sole survivor of her family's massacre. After she says her older brother Ben (Corey Stoll/Tye Sheridan) did it, she spends the next 25 years doing nothing and trying to forget about her painful past. But when a man (Nicholas Hoult) from a true crime club asks her to reopen old wounds, she begins to wonder if her brother is actually innocent.

Charlize Theron as Libby Day

If you haven't seen the film's trailer, be sure to watch it ASAP.

I recently watched the film, and — based on my memory of the book — the adaptation stayed true to all the main points, which is pretty rare nowadays. Unlike with "Gone Girl," Flynn didn't write the screenplay for this film, instead passing the torch over to Gilles Paquet-Brenner.

Fair warning: If you're just looking for another "Gone Girl," then this film is going to disappoint you. "Dark Places" is its own story, in its own world, separate from that of "Gone Girl."

Tye Sheridan as Young Ben Day

Of course, there's PLENTY of f–ked up stuff happening in this film: Satanic rituals, child molestation accusations, people obsessed with serial killers and, of course, a brutal family massacre. Like with "Gone Girl," there's a fantastic twist, which Flynn apparently came up with AT THE VERY LAST MINUTE.

Flynn said in an interview with ABC News her twist came from "not outlining or writing in any sort of efficient manner." She went on to say, "Literally when I was writing it, I was, you know, 30 pages from the end, going like, 'I wonder who did it?'" 😳

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The book and film's fictitious "Kill Club" apparently has its own website that lists unsolved and wrongfully convicted crimes. Flynn shared the link on her Facebook page back in July — and the site's still functional.

Pascal Le Segretain / Getty Images

So, what's next for Flynn? Adapting her debut novel "Sharp Objects" to the small screen, that's what! Very little information about the project has been revealed since the beginning of this year, but hopefully more information will be announced soon!