In Beatriz Williams’s latest solo novel, Summer Wives (Morrow, July), a young woman enters elite 1950s society on a secretive island. The bestselling author channels her experience as an outsider when her husband’s family first brought her to an exclusive members-only beach club.

“I was an anthropology major in college, so I’m fascinated by these little micro-cultures, where different people who are brought together have to find a way to get along,” says Williams.

She remembers sipping rum Southsides on the boardwalk with her mother-in-law, when an older man stopped to chat. “They talked about kids and lacrosse and Paine Webber. He walked away and my mother-in-law said, ‘I never liked him.’ And I thought, ‘Gosh, you could have fooled me!’ So, you have all these unspoken thoughts—90% is going on underneath the surface. It’s a very tight-knit culture, and I found this whole WASPy, East Coast culture fascinating.”

Williams’s fictional Winthrop Island is based on Fisher Island on Long Island Sound, which is visible from her Connecticut home. “It was hard to research,” says Williams, “because there’s such a code of silence and privacy there. What struck me is this relationship between the locals and the summer families that is symbiotic—they both obviously need each other—but there’s also this sense that, ‘We protect our own,’ whichever side of that divide you are on.”

As with her previous novels, Summer Wives showcases life in a different era. “What I like to do in all my books is say, ‘Hey, here’s a slice of who we were 30, 40, 50 years ago.’ I’m also trying to tell this larger story of the whole cultural transformation that took place in the first two-thirds of the 20th century, where we go from 1900 to just a completely different world in the 1960s,” says Williams. “For this book, I contrast the summer of 1951 to the summer of 1969, because you’ve got the moon landing, the civil rights movement, feminism is taking hold, and you have a society that’s starting to value science and technology more than the liberal arts.” Williams is excited to attend her first BookExpo, which will involve promoting not just her latest historical fiction but her upcoming historical mystery, The Glass Ocean (Morrow, Sept.), cowritten with Lauren Willig and Karen White, about three women with ties to the doomed RMS Lusitania. The three teamed up previously on The Forgotten Room.