Much like other young Brooklyn based writers, Lizzie Simon shuttles between her apartment in Carroll Gardens and an office in an artists’ collective in DUMBO. But the subject matter of her newest book, not yet titled, is a heavier one than many 28-year-olds would take on. The nonfiction project, which she calls “an older, more ambitious, more impossible cousin of ‘Detour,'” her first book, will explore the mental health of soldiers returning from Iraq.

She hopes that when it’s published, her hard-won success will have granted her some literary capital.

“I’m hoping that the one thing that I earned through ‘Detour’ working and from people liking it and liking the mix of it, is that I don’t have to do all that fighting next time around.”

“Detour” intimately chronicles Ms. Simon’s personal battle with bipolar disorder. She was 17, studying abroad in Paris, when she had a psychotic break. She saw enemies on the Metro and microphones in her bedroom. She announced in her English class that “The Invisible Man” was a hoax and in a manic flash she discovered why Mona Lisa smiles. Family friends sent her home alone on a plane, where she tried to open the emergency door mid-flight. When she arrived in America, she refused to complete her embarkation card because the paperwork didn’t include a box labeled “cat” under gender.

It’s hard to imagine Ms. Simon as she is now, munching on a bagel sandwich in a Brooklyn coffee shop, as a young girl who stopped eating altogether because she believed the CIA wanted to poison her. But that harrowing period, and her recovery from it, led to the publication of “Detour.”

After receiving her bipolar diagnosis, she was treated successfully with lithium. She enrolled at Columbia University on schedule that fall. After graduation, she worked as a producer at the off-off-Broadway Flea Theater on White Street, where she produced the Obie Award-winning kabuki play “Benten Kozo” with director Jim Simpson. All was well.

And yet. “The subject of my illness would come back to me in my own head,” she says. “I really couldn’t talk about it to anybody.” One day, riding the subway, she saw a poster that was part of a campaign by the New York City Department of Mental Health. “For People with Mental Illness,” it read, “Treatment Is Working.”

The sight prompted another break, but this time it was of a different nature.

As she writes in “Detour,” “The posters are everywhere. So in the morning as I go to the Flea and in the evenings when I return home, I see those posters, and every day I thank God that someone is out there working on this stuff. I begin to wonder why I’m not. There’s so much to be done.”

She quit her job, which she loved despite its high stress level. “You’re basically the worrier on a massive project,” she says, describing her work as a producer of music, dance, and theater programs. “Everyone does their role, and you worry. So for someone who’s prone to depression and anxiety … I’m really good at worrying, but that doesn’t mean I should do it.”

She took on a project that would cause even more worry, anxiety, and depression – but would ultimately change her for the better. “I fell in love, I developed a sense of compassion for what I’d been through that has carried me ’til today and will always carry me.”

Ms. Simon borrowed her father’s Nissan Pathfinder and embarked on a six-week solo road trip in which she visited other young people whose bipolar disease had been successfully treated. Departing New York, she traveled to Rhode Island (her home state), then down the eastern seaboard to the South, where she cut across through Texas, up to Los Angeles, and back to New York.

Never more than one step ahead of herself, she found people to interview by calling friends of friends and contacting mental-health facilities. She marvels now at how little planning went into the cross-country tour. “I was really young and really impatient. I thought that if I took too much time before the trip, someone would convince me not to do it or something like that, and I really wanted to go. It was a little bit escapist. It made it a lot harder.”

Her first interview, conducted in New York at Pete’s Tavern, was with Nicholas Berenson, a bipolar man addicted to drugs. She also spoke with a Virginia radio D.J. who bought $200 worth of purple embroidery thread during a manic episode; a shy 16-year-old who stole credit-card numbers from her mother’s business, and a student who swore at an Army major during ROTC summer camp. All of them emerged from drug treatment and therapy with tools to manage their illness. Ms. Simon reports that, so far, their stories all have happy endings.

When she started out on her trip, Ms. Simon knew she wanted to write a book about it. She thought it would probably turn out to be a Studs Terkel-style collection of interviews. Instead, “Detour” is as much about the writer as it is about her subjects. She covers her romantic relationship with Mr. Berenson in detail. The writing style is almost stream-of-consciousness, full of one-sentence paragraphs and one-paragraph chapters. It’s stuffed with interjections such as “WHAT!! EVER!!” and “Breathe.” Many chapters end with “Wait. Stop.”

“It wasn’t until I had a book published that I thought, maybe I can be a writer,” she says. “The book is not at all like Studs Terkel,” she adds, laughing.

She wrote it without an agent, secured one with some difficulty, and then began the long process of finding a publisher. “My agent actually submitted it over 35 times over the course of a year. It would go out, and then I’d get eight rejection letters; it would go out, and I’d get eight more. It was devastating…I had quit a career that was very successful to do it, and I just felt like such a failure. They just didn’t get it.”

Despite the struggles, she found her audience. The book has been optioned for film – Ms. Simon hopes that Keisha Castle-Hughes of “Whale Rider” plays her. She’s also gotten feedback on her choice of vehicles. “I got a lot of letters from people saying, like, ‘How can you drive an SUV? Don’t you care about the world?'” She sympathizes. “I’m very much against SUVs [now] and I didn’t understand that then.”

Thousands of readers who have been encouraged by her story write to her – so many that “I’ve had to cut it off at this point.” She explains on her Web site: “As much as I would like to be there for you or your loved one during this time of extreme duress and need, I am not able to do so.”

She had anticipated certain battles, but was surprised at the haggling with bookstores about where the book should be shelved.

“What I do is narrative, it’s personal, it’s psychological, it’s scientific, it’s journalistic, it’s scholarly,” she explains. “I think that’s what makes it sort of interesting and special, but for publishers and booksellers it makes them crazy. They don’t know where to put it and they don’t know how to describe it.”