Competing against the world’s top travel guides as a self-published author and succeeding isn’t easy. Publishers such as Fodor’s, Rick Steves, and Lonely Planet invest big bucks researching and publishing full-color guides to cities and countries all over the globe. But the copywriter, content strategist, and world traveler Gigi Griffis found a niche with her 11 self-published travel guides, which have all been top-100 bestsellers in their respective Amazon categories.

What does her series offer that the others don’t? The clue is in the subtitles: 100 Locals Tell You Where to Go, What to Eat, and How to Fit In. Contributors to the guides include food writers, tour guides, winemakers, photographers, teachers, mountaineers, and shopkeepers—all dishing their secret tips for the best way to authentically see their cities. “Everyone wants to have a best friend in Paris to show them around,” Griffis says. In a category crowded with big brands, she has filled a gap.

Griffis knew that if she wanted to launch a successful travel series, her books would need to offer something new, which meant ditching impersonal information in favor of a more chatty, intimate feel that focused on giving locals a voice. That means that Griffis’s guides don’t include hotel listings, currency information, or restaurant rankings. “That information is well covered, and trying to cover it myself would have simply been reinventing the wheel,” she says. Those other guides “don’t tell you the town winemaker’s favorite places to drink or the weekend mountain guide’s favorite hiking trails,” she says.

Griffis’s Italy guide, for example, offers readers tips from locals on how to spot authentic gelato, how to avoid pickpockets and local scams, and when not to wear flip-flops, and explains why you shouldn’t order a cappuccino after lunch. Rather than competing with the big brands, her series has found its niche as a companion to them. On Amazon, her Italy guide is frequently bought with Rick Steves’ Italian Phrase Book and Dictionary, as well as Rick Steves Italy 2017.

“Know when to DIY, when to hire, and when to trade,” says Griffis to other aspiring self-publishers. For her first guide, she traded her skills as a copy editor in return for a book cover design. She did the same in return for editorial feedback on the book. “Instead of hiring one editor to edit the whole guide, I found five or six and asked each to take a section of the book—a much smaller ask,” she says. As she already knew how to write code, she used a free software program called Calibre to format her e-books using HTML.

Publishing books of this size is no easy feat. Griffis’s most comprehensive guides (interviews with 100 locals for $21.97), for Italy, France, and Switzerland, each run more than 300 pages and are priced in line with traditionally published travel guides. Each of the smaller city guides—to Barcelona, Denver, New York City, Paris, Phoenix and Tucson, and Prague—is priced at $9.99 and includes interviews with 10 locals. The next step after publishing the books was getting the word out.

Griffis says one of her most effective marketing strategies was securing Amazon reviews; for this she targeted only top reviewers on the site. Each reviewer has a profile, and many of them provide email addresses or ways to contact them if you are interested in honest reviews, Griffis explains. She reached out to about 30 people, which resulted in honest critiques of her titles.

Griffis’s guides to Italy, Prague, and Switzerland have all hit the top 10s in their respective Amazon categories. And she notes that the royalties from her book sales cover anywhere from 35% to 100% of her monthly expenses. “I talk about how I make money while traveling because I want more people to feel like they can do that, too, if they want,” Griffis says.

Jennifer McCartney is a freelance writer and editor, and the author of the novel Afloat.