What goes into making the perfect beach read for a Maine summer? Just as everyone has a different recipe for a good clam chowder, the answers may vary. But certain ingredients remain the sine qua non of summer reading.

Whether you are looking for something light and frothy or something dark and compelling, there must be a mystery lurking at the heart of the story. Think of it as the clam in the clam chowder.

Usually that clam takes the form of a crime. “Murder is very important to the beach reach,” says Marion Fearing, manager of Sherman’s Books in Portland. “Has a character witnessed a murder? Did the main character’s spouse get murdered? Whatever happens, someone is dead and someone has to figure out why.”

“One of my favorite tropes is the ominous plotline juxtaposed against the bright, clean, hopeful setting of the ocean air and sandy beaches,” says Rebecca Morton, owner of Back Cove Books, which is slated to open this fall in Portland. “The body of a beloved town member washes ashore in the early morning hours and of course secrets, debts and grudges are all revealed.”

If not a murder, it could be a secret that lurks. The other great beach read genre is the romance, and secrets are the premise of every single one of them. Think fish instead of clam chowder.

A careful reading of book jackets reveals a positive pandemic of secrets: dark secrets, shared secrets, small town secrets, scandalous secrets, and secrets from hidden pasts. Keeping all these secrets can involve some heavy lifting. Witness the plight of the struggling heroine of bestselling author Meg Mitchell Moore’s “Vacationland,” who has both “a past she’s trying to outrun” and “a secret she’s trying to unpack.”

But nothing tops the “family secret” for sheer summer box office appeal — unless it is the “generational family secret.” This was the plot-driver in 2019’s summer must-read, “The Guest Book” by Sarah Blake, which featured generations of WASPy bluebloods on a (thinly veiled) island of North Haven with a closetful of, well, dark family secrets.

And what is a beach romance without a romance? “Two people have to fall in love,” decrees Fearing. “Doesn’t matter what time period or setting.”

But with whom? It has to be a “brooding, mysterious love interest that sees the world differently from everyone else!” says Antyna Gould, Sherman’s of Rockland bookseller. “Complete with an ‘I just rolled out of bed and threw on somewhat clean clothes but look effortlessly good in them’ wardrobe and an ironically sarcastic sense of humor.”

The secondary characters are also important. As a chowder needs salt, so does a beach read need a colorful character. Preferably a wise and salty old lobsterman, as in the father figure in Linda Holmes’s debut novel “Evvie Drake Starts Over,” set in the Rockland area.

When it comes to plot, it doesn’t have to be either/or, according to Fearing. In fact, “the best beach read is when both romance and murder is combined. It’s perfection,” she claims, citing Colleen Hoover’s popular romantic thriller “Verity” as an example.

Which brings us to what is the most definitive ingredient in any chowder — or rather, beach read: its setting. While a few mysteries may take place in the wilderness (Paul Doiron’s game warden series set in the North Woods) or a city (as in Bruce Coffin’s Portland detective books), it is essential that a romance be set by the sea, more specifically in a “seaside village.” Or “small town.” Either way, it must be picturesque.

Islands, especially if they are wreathed in fog, also loom big in the popular romantic imagination. And don’t forget those other crucial elements of the setting, notes Sherman’s of Bar Harbor manager Katie Lieberman: “the lighthouse, a sailboat and a lobster boat.”

It’s crucial that the village contain a “summer cottage” that’s been owned for generations and is thus well stocked with dark secrets. So, ideally: a family cottage in a small and picturesque seaside village on a misty island populated by salty lobstermen. With a lighthouse.

Apparently suburban Maine is not a place where either crime or romance can flourish. So, take note, you lovelorn and felonious Cape Elizabethans. Time to set sail for Monhegan.

A beach read title has to contain some of those same words to evoke the setting. “Title trends come in waves,” explains Sherman’s of Damariscotta bookseller Megan Hawkes, using an apt metaphor. “A few years ago it was all ‘The Light at the End of the Tunnel Between Oceans.’ ” Before that, “everything was the Wife or Daughter of some innocuously titled profession.” But titles with the words “Sea or House or Summer,” she concludes, “are perennials.”

The only fly in our summer beach read soup recipe is the fact that, while Maine has 3,500 miles of open coastline, only 2 percent of that — 70 miles — is actual sand beach. That’s a lot of rocky coast.

That may explain why some Maine authors have a slightly different take on the summer book.

Alice Greenway’s novel “The Bird Skinner” was dubbed “a thrilling evocation of young love” by the New York Times and was set in romance-novel heaven (North Haven Island, where Greenway lives). It even features a wise and crusty old man. But it is far more complex than a summer beach read. As is its author. Her first suggestion for a beach book was “Kafka.” When pressed, she admits she likes to stuff a small volume of Zen nature poems into a picnic basket, lie on a rock by the shore and read them aloud to “remind me why I come to a beach in the first place.”

Mexico, Maine, native Monica Wood has never set a story anywhere near a “seaside village,” favoring Portland or mill towns for her novels. Instead of beach reads, she is always on the lookout for what she calls a good “hammock read.” “Not everyone,” she points out, “lives in a rose-covered cottage” on the ocean.

Her ideal hammock read is a “page-turner about a perfect-crime”— a clever, non-violent, well-crafted puzzle — to lose yourself in while someone is grilling dinner in the backyard of a cottage overlooking a lake or stream. Which also count as locales for beach reads. Wood’s favorite beach/hammock authors include Gerry Boyle and “all of Paul Doiron.”

A final key ingredient, for Mainers at least, is authenticity. Mainers don’t want to eat Manhattan clam chowder. Similarly, “they really want books set in Maine, written by Maine authors,” says Katherine Osborne of Letterpress Books in Portland. “And they can tell when it’s written by someone who lives in Iowa.”

This brings us to the last plot point — the ending. “Does the couple make it to the end?” asks Fearing. “Yes, of course they do.” Is the crime solved and the bad guy apprehended? Inevitably. “No matter how problematic the actions of the characters are,” she asserts, “it has to be a happy ending.”

So sit back, relax and, as one jacket blurb says, “Let the waves carry you home.”

Amy MacDonald is a freelance writer and author who lives in Portland, and in a seaside cottage on Vinalhaven. She may be reached at AmyM781@gmail.