Barbara Mertz died at 85. (AP Photo/HarperCollins)

Barbara Mertz, an erstwhile Egyptologist better known to millions of readers as Barbara Michaels or Elizabeth Peters, the noms de plume on the covers of her dozens of top-selling historical mysteries and romantic thrillers, died Aug. 8 at her home near Frederick. She was 85.

Her daughter, Elizabeth Mertz, confirmed her death and said she did not yet know the cause.

Dr. Mertz was one of the most popular writers of her era and genres. Her oeuvre encompassed ad­ven­ture, romance, history, the supernatural and timeless themes such as the imprudence of standing in the way of a woman on a mission. She churned out books with extraordinary speed, once remarking that she had lost count of them sometime around the publication of her 50th volume.

She wrote more than two dozen novels as Barbara Michaels, the pseudonym under which she made her fiction debut with “The Master of Blacktower” in 1966, and more than three dozen as Elizabeth Peters. Those books included a long-running series about the parasol-toting Victorian pyramid explorer Amelia Peabody.

“Between Amelia Peabody and Indiana Jones, it’s Amelia — in wit and daring — by a landslide,” author Paul Theroux once wrote in the New York Times.

Dr. Mertz acknowledged that Peabody — the protagonist of books including “Crocodile on the Sandbank” (1975) and “The Last Camel Died at Noon” (1991) — was not unlike herself. Fascinated from a young age by the ancient world of the pharaohs, Dr. Mertz pursued a doctorate in Egyptology at a time when relatively few women sought and even fewer found professional career opportunities.

She wrote two scholarly books on ancient Egypt in the 1960s but was unable to find employment in academia. When she turned to fiction, she discovered that she had a talent, and that readers had an appetite, for particular tales of historical intrigue.

By weaving the curiosities of ancient Egypt, archaeology and other rarefied fields into her fiction, Dr. Mertz produced one crowd-pleasing yarn after another.

Her fiction, Washington Post writer Sarah Booth Conroy once noted, was “the literary equivalent of multiple gin-and-tonics.” They were “to be taken in times of self-indulgence, physical pain or mental anguish because they come with a guarantee that the evil will be punished, the good will be rewarded, pleasingly plump women will seduce brilliant men with bulging muscles and all will be set right in the world.”

Besides her debut novel, Dr. Mertz’s early Barbara Michaels volumes included “Sons of the Wolf” (1967), “Ammie, Come Home” (1968) and “Someone in the House” (1981). More recent releases included “Vanish With the Rose” (1992), “Dancing Floor” (1997) and “Other Worlds” (1999). Dr. Mertz described the books as “thrillers, many with a supernatural element.”

Elizabeth Peters debuted with “The Jackal’s Head” (1968), and her books tended more, Dr. Mertz said, to “mystery suspense.” Serialized heroines, besides Amelia Peabody, included art historian Vicky Bliss in such books as “Borrower of the Night” (1973) and “Trojan Gold” (1987) and Jacqueline Kirby, the librarian-turned-romance novelist of “Die for Love” (1984) and “Naked Once More” (1989).

Many readers found, and Dr. Mertz seemed to acknowledge, that Elizabeth Peters was the funnier of the alter egos. In economic terms, she explained: “Peters supplies me with a comfortable living. Michaels buys me lily ponds and gazebos.”

Dr. Mertz joked about the “nuisance” — including hotel and airline reservation mishaps — created by her tripartite identity. But by dividing her output between pen names, she could shield herself from condescending critics for whom “prolific,” she remarked, was a “nasty word.”

Barbara Louise Gross was born Sept. 29, 1927, in Astoria, Ill., and grew up in Oak Park, where she went to the high school Ernest Hemingway had attended. Years later, she remarked that his “sparse style” didn’t “appeal” to her.

She became enchanted with Egypt as a teenager after her aunt took her on an outing to the Oriental Institute at the University of Chicago, where she would later receive a bachelor’s degree in 1947, a master’s degree in 1950 and doctorate in Egyptology in 1952.

Learning of her area of specialization, her parents asked — “with perfectly good sense,” Dr. Mertz said — “what are you going to do with this?” When she and her husband, Richard Mertz, came to the Washington area in the 1950s, she found it easier to obtain secretarial work if she omitted her doctorate from her qualifications.

Her husband’s government career took them to Europe, where together the couple wrote “2,000 Years in Rome” (1968). Along with her books “Temples, Tombs and Hieroglyphs” (1964) and “Red Land, Black Land” (1966), it was one of the few books published under her real name.

Her first pen name, Barbara Michaels, was the invention of her then-agent. Dr. Mertz often remarked that she was so happy to be published, she would have accepted “Jack the Ripper.”

After she and her husband divorced, fiction-writing allowed Dr. Mertz to support herself and her daughter and son, whose combined names created her second nom de plume. Survivors include her two children, Elizabeth Mertz of Skokie, Ill., and Peter Mertz of Carbondale, Colo.; a sister; and six grandchildren.

Dr. Mertz lived for many years near Frederick in what The Post described as a “wonderful, haunted, 1820 stone house.” She had a predilection for cats, a least a few of whom she named after Egyptian pharaohs and Washington Redskins players.

As a writer, she prided herself on offering readers a classy sort of romance even while assuring them that Amelia Peabody and her husband Radcliffe Emerson would continue to enjoy the carnal pleasure “until they’re 90.”

“I have a theory about sex scenes,” she said. “I start them on track and let the reader’s imagination take over. One of my biggest compliments was, ‘You never use a word that would make my grandmother blush. But that tent just steams.’ ”