Last summer, a book changed Kohn Glay’s life.

A TikTok ad had steered him to “The Shadow Work Journal,” a slim workbook that directs readers to explore hidden parts of their unconscious — their shadow selves, in the book’s vernacular. He ordered a copy, and soon was back on TikTok, fervently recommending it to his followers.

“If you’re on your spiritual journey, you absolutely need to go and get you one of these,” he says in the video, urging viewers to buy the book in the TikTok store.

The video went viral, eventually drawing more than 58 million views. Glay, who is 43 and lives in Baltimore, began holding online classes to guide people through the journal. Over the next few months, people who watched his videos bought more than 40,000 copies of the book on TikTok, and Glay earned more than $150,000 in commissions. By December, he had quit his job as a sales representative for Home Depot and now runs his own business, “Happy Healin,” which offers subscribers spiritual mentorship and coaching through Zoom sessions.

Glay is part of the army of TikTok influencers who helped turn “The Shadow Work Journal” into a mega best seller. He’s so closely associated with the book that people often assume he wrote it. “It became a daily thing to tell people I’m not the author,” he said.

The real creator of “The Shadow Work Journal” is Keila Shaheen, a 25-year-old writer from Texas with a background in marketing who self-published the book in 2021, and has since been crowned “the self-help queen of TikTok.”

After the journal blew up on TikTok, Shaheen went on to sell more than a million copies. Most of those — nearly 700,000 copies — were sold through the TikTok shop, and were marketed relentlessly by passionate influencers like Glay, who earn a 15 percent commission on each sale from Zenfulnote, Shaheen’s company.

Shaheen’s unusual path to bestsellerdom shows how radically book marketing and sales have been changed by TikTok. Over the past few years, publishers have frantically rushed to harness the power of the platform as viral videos and reviews by influencers have propelled sales for blockbuster authors like Colleen Hoover, Emily Henry and Sarah J. Maas.

But Shaheen is perhaps the first self-published nonfiction author to break out in a big way on the platform, a feat she accomplished by fully harnessing its potential not just for marketing, but for direct sales.

Her stunning trajectory has left many authors and publishers wondering whether that formula can be replicated, and how publishers can navigate the new online retail ecosystem — a fast moving, algorithm-driven marketplace that threatens to cut them out entirely.

“To think that she achieved a million copies sold in the United States alone, without a publisher, without any international expansion, without brick and mortar support, it breaks all the rules of what makes a best seller,” said Albert Lee, a literary agent with United Talent Agency, which represents Shaheen.

Others wonder just how much bigger Shaheen’s self-help empire can get. Earlier this year, Shaheen signed a five-book deal with Simon & Schuster, after months of being courted by big publishing houses.

Simon & Schuster won her over with an unusual arrangement: a seven-figure advance, plus a 50-50 profit share. Publishers typically give authors an advance and then a 15 percent cut of royalties if they earn back the advance. The deal included a new, expanded edition of “The Shadow Work Journal,” which was released in late April, with a first printing of 100,000 copies, plus two new books by Shaheen.

“We really wanted to show Keila that we had a long-term vision,” said Michelle Herrera Mulligan, the vice president and associate publisher of Primero Sueño Press/Atria, the Simon & Schuster imprint that signed Shaheen. “There is still a huge untapped audience for this book.”

In person, Shaheen comes across as soft-spoken and reserved, not as a hyper-driven entrepreneur or a charismatic wellness guru.

During an interview in late April at a restaurant in Midtown Manhattan, Shaheen seemed slightly stunned by the flood of attention, and money, that her book has generated. The next day, she appeared on “Good Morning America” to promote the new edition of “The Shadow Work Journal,” then had meetings at her publisher and literary agent’s offices.

Shaheen, who has suffered from acute social anxiety in the past, was surprised by how calm she felt, she said.

“I’m a huge introvert, so that was a testament to how much I’ve grown,” she said.

Shaheen first encountered the idea of shadow work in 2021, when she was feeling anxious and adrift in the wake of the pandemic. After graduating from Texas A&M in 2020 with a degree in business and psychology, she found work in online retail and marketing — including a stint as a creative strategist for TikTok. Coming out of the isolation of Covid, Shaheen felt disconnected, and found working in a corporate environment overwhelming.

One day, while searching online for therapeutic journaling prompts, she came across references to the Swiss psychoanalyst Carl Jung’s idea of the shadow self, which holds that parts of our unconscious can mask hidden fears and desires. She learned about a practice called shadow work, a somewhat fringe field that draws on Jung’s ideas to guide people as they interrogate their shadow selves, with the goal of accepting parts of themselves that make them feel guilty, ashamed or afraid.

Shaheen started posting videos on Instagram and TikTok about shadow work exercises she was trying, and began getting messages from viewers asking for a printed guide. So in the fall of 2021, she self-published the journal, and began selling copies for $19.99.

The first edition — which didn’t even have Shaheen’s name on the cover — was a slim paperback that guided readers through shadow work with interactive exercises, including Mad Lib-style fill-in-the-blanks (“As a child, I was told not to ___, this made me very ___”), inner child affirmations (“I am protected”) and journaling prompts (“What is your biggest fear in life?”).

Sales were slow at first. Then, in late 2022, TikTok expanded into online retail. The platform started selling products directly through the app, and created an affiliate program, which allowed influencers to post videos about products in the store and earn a commission. Once Shaheen started selling the journal through TikTok, requests came pouring in from influencers who wanted free copies in exchange for video promotion.

TikTok was soon flooded with emotional videos of users filling out the journal’s pages; some gushed that the journal is cheaper than therapy.

The journal also drew some skepticism. Some on social media attacked shadow work as anti-Christian and even demonic. Others said it failed to live up to the hype, or complained that their feeds seemed to be wallpapered with ads for the journal.

Still others questioned Shaheen’s credentials as a mental health guide. Shaheen — who is described in her author bio as “a certified sound healer and behavioral therapy practitioner” — completed an online training course in cognitive-behavioral therapy, but is not a licensed therapist.

Some experts in Jungian psychology worry that “The Shadow Work Journal” oversimplifies Jung’s ideas.

“My concern about it is that the shadow is really complex,” said Connie Zweig, a retired psychotherapist who has published several books on shadow work. “It can be risky to go exploring in the dark without guidance, without expertise.”

Shaheen said that she always intended the journal to be an introduction to shadow work, not a comprehensive guide.

“The journal is meant to be a bridge,” she said. “I wouldn’t say that it’s created to replace therapy.”

By September, the book hit No. 1 on Amazon. In October, Shaheen met with two agents from United Talent Agency, Rebecca Gradinger and Albert Lee. The agency could help her build an international audience and get her book in physical stores, they told her.

Shaheen signed with them about a week before the Frankfurt Book Fair, the largest fair for international rights in publishing, and the agency then sold translation rights to “The Shadow Work Journal” in 27 countries, Lee said.

Shaheen was still reluctant to hand over U.S. rights to “The Shadow Work Journal.” She was already a best seller, and “the initial offers weren’t compelling,” she said. Her agents agreed that a typical publishing deal might not benefit her.

“Keila’s at the vanguard of unlocking this entirely new market and ecosystem,” Lee said. “It became very obvious that in traditional publishing, we were all well behind what Keila was doing.”

Shaheen was swayed by Primero Sueño’s profit-splitting offer, which came with a plan to publish and market Spanish-language editions. Shaheen, whose father is from Puerto Rico and whose mother is from Brazil, saw the potential to expand her reach among Spanish speakers.

It’s still unclear whether “The Shadow Work Journal” will catch on with a wider demographic, or if it owes its popularity to a viral trend that has waned. So far, the new edition has sold nearly 18,000 copies, according to Circana Bookscan — a healthy amount, but hardly a hit.

Herrera Mulligan, Primero Sueño’s publisher, said “The Shadow Work Journal” is just the beginning: “We really want her to be the new empress of self-help.”

Primero Sueño is now aiming to saturate the self-help market with Shaheen’s books, and has set an aggressive publishing schedule, releasing two more of Shaheen’s self-published titles this year — one in July, another in October. The titles, along with her poetry collection, are big on TikTok and have sold around 100,000 copies collectively on the platform.

She is also working on two new books: one about the origins and applications of shadow work and another titled “The Light Work Journal,” which prompts readers to reflect on and enhance their strengths.

And Shaheen, no longer held back by social anxiety, seems ready to embrace the spotlight. Unlike the first edition of “The Shadow Work Journal,” the new edition features her name in large font — under a banner that says “more than 1 million copies sold.”