“It was a dark and stormy night,” said Cynthia Riggs, recalling the conception of her first novel written more than 30 years ago. She was living on a houseboat in Washington, D.C., at the time, and along with her neighbors on the dock, she was sick of the commodore.

At one of the houseboat parties she often attended with the neighbors, someone suggested killing the commodore off. Not in real life, but metaphorically, as a character in a novel. Someone else suggested that Ms. Riggs, who had written for a local newsletter, do the deed. “I thought writing a book was a monumental task,” the author said recently, seated behind her desk in the upstairs study of her home in West Tisbury.

“Only authors write books, and I was no author. So I just started putting one word after the other, and it ended up being a book.”

But she was unable to find a publisher at the time, and the manuscript for Murder on C-Dock sat untouched for many years.

In 1998 Ms. Riggs went back to school at the age of 68 to earn an MFA in creative writing. Since then she has published 11 novels and has developed a national following. A 12th novel in her Martha’s Vineyard Mysteries series, Bloodroot, is slated to be released in 2016. The most recent Martha’s Vineyard mystery, Poison Ivy, will be re-published in hardcover next year.

That series features the poet Victoria Trumbull, who remains 92 years old, despite each novel taking place in the present. In her MFA program, Ms. Riggs studied the ways in which various mystery writers handled the passage of time, including those whose main characters never age. “As long as you play fair with your reader, you let the reader know this is what I’m doing, the reader is willing to go along with that,” she said.

Around 2001, after having some initial success as a novelist, Ms. Riggs pulled out the old manuscript of Murder on C-Dock. After re-reading it, she thought it had promise. Most of all, she could now see where the book could be improved.

“I saw a lot of weaknesses that new writers have, like too much description or too much of something and not respecting the reader’s intelligence,” she said. “Giving too much away because you think you have to explain everything.

“I figured the strength of the book is it’s a part of Washington not many people know,” she said, adding that the people around the dock living on houseboats were an unlikely group. “Everything from gas station attendants to senators . . . and the only thing they have in common is this boat life. There were two things we were really worried about. One was fire and one was somebody falling overboard.”

Much of the inspiration in revising her novel over the years came from her Wednesday night writers’ group. “I’d get these comments that my protagonist was not strong enough, wasn’t somebody they really liked, and I didn’t like her either,” she said. She ended up rewriting the protagonist altogether, modeling her after a friend in the group who ran marathons.

Murder on C-Dock marks the beginning of a new mystery series featuring Percie Lee Butler, a young divorcee who lives on a houseboat on the Potomac River.

Almost all of Ms. Riggs’s characters are derived from real people. “If you go through my books, you’ll find out that most of them are people we know on the Vineyard,” she said. “I kill off everybody I’m mad at.”

She self-published the new novel this year through Cleaveland House Books, named for the historic bed and breakfast where her family has lived for eight generations.

Her small upstairs study is lined with books of the trade: Detectionary, Forensics for Dummies, Deadly Doses: A Writer’s Guide to Poisons. It also includes a collection of poetry by her mother, Dionis Coffin Riggs, and other books that Ms. Riggs has self-published over the years. Arrows and Snakeskin, a young adult novel by her father, Sidney N. Riggs, is used as a textbook at Westchester Community College in New York.

Propped up in a field near the house is a large wooden boat, a reminder of the years Ms. Riggs lived on the water. As a child, she dreamed of living on a houseboat, or in a train caboose. “And a caboose was sort of out of the question,” she said. “But a boat was imminently feasible.”

What drew her to that life was the freedom of it, she said. “The freedom and the fact that if you felt like doing it, you could just let go the lines and take off. Living on a small houseboat also required living simply. “If you bought something, you had to get rid of something of equal size,” she said. “It was an absolutely wonderful life.”

As a licensed captain in Washington, D.C., she led tours on the Potomac River. She later bought a trawler so she “could really go places” and would travel down to Chesapeake Bay. “I guess I have the salt water in my veins, because my forebears were seafarers,” she said.

Back in the family home, she recently started a new phase of life.

She married her second husband, Howard Attebery, a microbiologist and retired forensic photographer, about a year and a half ago. The couple is now putting the finishing touches on a book chronicling their relationship, which was rekindled after more than 60 years through letters and emails sent across the country.

“We were corresponding two or three times a day and sending photographs to each other and you could see this relationship building,” Ms. Riggs said. “Until finally we were really getting quite intimate and still hadn’t seen each other. So we put together a book describing the courtship.”

Murder on C-Dock is the first book where Ms. Riggs has used her hyphenated name — Cynthia Riggs-Attebery. She said the idea was to help distinguish the two series while allowing all of her books to stand together at libraries and bookstores. She will still use her maiden name for the Martha’s Vineyard Mysteries series.

She plans to start the next Percie Lee Butler novel in the near future. Some aspects of Percie Lee’s life, such as her relationship to her daughter and her love of running, were impractical to work into the earlier manuscript, so she hopes to bring them out in future novels, which will also be set in the D.C. area. “Running through the Washington area she can then comment on the scenery,” Ms. Riggs said. “Because the Washington scenery is really quite beautiful.”