Mermaids are having a moment that has lasted roughly a decade. The mania started around 2012, when sirens supplanted vampires in young adult fantasy, but the trend really took off in 2015, when celebrities took to Instagram in swimmable tails. Mermaid hair, mermaid fitness classes and mermaid food soon followed. Even in the midst of the current pandemic, people are drawing inspiration from Disney’s Ariel, looking longingly out their windows and singing #quarentinelife parodies of “Part of Your World.”

Mermaid mania is coming around to books again — but this time, the trend has broadened to include nonfiction titles for readers of all ages.

Despite their obvious appeal, mermaids are an uneasy fit for children’s literature. These are, after all, mythical beings who do not make very good role models. For centuries, traditional stories have portrayed mermaids as dangerous seductresses, with their hybrid bodies representing the peril and beauty of the sea, as well as the (supposed) irrationality of women.

So how do you tell these often plainly misogynistic stories in a modern, kid-friendly way? That’s the challenge faced by two new children’s books that survey mermaid tales from around the world: “The Very Short, Entirely True History of Mermaids,” by Sarah Laskow, and “The Mermaid Atlas,” by Anna Claybourne.

Both are awash in the blues and greens of the ocean, and they cover many of the same stories. Claybourne’s volume is the more lavishly illustrated, and it casts a wider net, depicting a menagerie of human-animal water spirits, including the duckfooted lamia of northern Spain and Vatea, the laterally split human/dolphin ancestor of Cook Islands inhabitants. “The Mermaid Atlas” also feels more organized, orienting young readers (ages 7-11) with a map at the beginning of each section.

The stories are repetitive at times, and even a little dull — a byproduct, perhaps, of glossing over kid-unfriendly details. For instance, she omits the rather crucial plot point that Ireland’s selkies (beings capable of shifting from seal to human form) only marry men under duress, after having their seal skins stolen. Likewise, her account of Eastern Europe’s rusalkas skips over their origins — they are often the ghosts of girls who were murdered near water — and jumps straight to how these vengeful spirits drown young men, which feels a little unfair to the rusalkas.

Laskow, science editor at the Atlantic, takes a more unflinching look at the dark side of mermaid stories. She doesn’t shy away from the fact that selkie husbands are thieves and abductors. She also provides readers (ages 8-12) an anthropological framework for understanding the preponderance of mean mermaids in these tales: “People believed that mermaids were so charming they were hard to resist, and could convince humans to do things they weren’t supposed to. Some medieval Christians believed that mermaids wanted to capture their souls! Stories like this were a lesson.”

Laskow’s book also devotes many pages to modern mermaids and science lessons on mermaid topics. I particularly enjoyed her interview with a biologist about how mermaids might breathe underwater. (They’d need gills, which they’d have to keep moist all the time, even when gallivanting on land.)

Both books show that mermaids have always been a diverse group — a necessary corrective given the ugly #NotMyAriel backlash after Disney cast an African American actress as the lead in the hotly anticipated live action “The Little Mermaid.” If there’s one thing all mermaids have in common, it’s their mutability. These are hybrid creatures who have one foot (fin?) in two different worlds. No wonder, then, that they’ve become an avatar for people who occupy liminal spaces, like adolescent girls and, more recently, transgender folks.

Jessica Love’s 2018 stunner, “Julián Is a Mermaid,” (age 4 and up) taps into that cultural current, with a story about a little boy who sees people dressed as mermaids on the subway and decides to dress up himself. After a suspenseful moment during which Julián’s abuela (grandmother) finds him in feminine garb and seems to turn away from him, she returns with a necklace for Julián, then takes him to the Coney Island Mermaid Parade. It’s this vision of acceptance — and the extravagant beauty of the sea, as seen through Julián’s daydreams — that provides a refreshingly modern alternative to traditional mermaid tales.

Reading all these kid-friendly mermaid books left this adult reader wishing for juicier fare — and I slaked my thirst with two recent nonfiction titles, Carolyn Turgeon’s 2018 book “The Mermaid Handbook: An Alluring Treasury of Literature, Lore, Art, Recipes, and Projects” and the 2019 folklore anthology, “The Penguin Book of Mermaids” (edited by Cristina Bacchilega and Marie Alohalani Brown). Bacchilega and Brown’s volume brings together dozens of tales from a diverse array of cultures, including three that have never before appeared in English. The authors leave interpretation largely to the reader, but they do provide a compact overview of the genre, noting that mermaids “reflect our fascination with and fear of female bodies and of water and our dread of predators or poisonous creatures that live in or near water. But such tales are also social and cultural commentaries about what it means to be human: they encapsulate our beliefs and mores, express our weaknesses and strengths, and expose our deepest fears and desires.”

Turgeon also surveys mermaid tales, but hers is a more lyrical volume, one that includes odes to mermaids by Tennyson and Shakespeare and luscious paintings by Botticelli and Klimt. A novelist, Turgeon summarizes mermaid folklore with a keen eye for symbolism and a gift for plain, nonacademic language. “The Mermaid Handbook” also extensively covers mermaids in modern American culture — from Annette Kellerman’s (tragically lost) early 20th-century movies to the advent of the “mermaid gown” silhouette in the 1930s and onward to the modern mermaid movement, in which people of all ages, sizes and gender identities embrace their inner sea goddesses. Mermaids, it seems, surface and retreat as they please, but they are always with us. Long may they reign.

Sadie Dingfelder is a writer in Washington.