Love, Italy, and alternative-history fiction that travels down a what-if path to approach a truth: these have long been preoccupations of Christopher Castellani. His first three novels, the Maddalena trilogy (A Kiss from Maddalena, The Saint of Lost Things, and All This Talk of Love), were published by Algonquin over a 10-year period beginning in 2003 and form a semi-autobiographical family memoir. Castellani says the “alt” elements took root because he wanted to give his parents access to the people and things they’d felt the most regret about. For his mother, Castellani wrote in the boyfriend she always wished she’d had before marrying at 19 and immigrating to the United States from Italy; for his father, the restaurant his wife wouldn’t let him open.

Those same three preoccupations dominate Castellani’s new novel, Leading Men (Viking, Feb.)—although the love featured is a more tempestuous form whose bearers throw plenty of recriminations and grenades at each other (think Elizabeth Taylor and Paul Newman in Cat on a Hot Tin Roof). The novel is based on the 15-year on-off relationship between playwright Tennessee Williams and former truck driver Frank Merlo, which ended with Merlo’s death from lung cancer in 1963. Though Williams continued to write plays afterward, he didn’t write another Broadway hit.

The novel, Castellani says, had been gestating since 1997, when he read Dotson Rader’s memoir, Tennessee Williams: Cry of the Heart, which he found at a used bookstore in Wilmington, Del. Castellani observes in a note to the reader that, as a gay Italian, he felt an “instant kinship” with Merlo, a working-class gay Italian guy from New Jersey. Merlo gave Williams the stability he needed to create some of his best-known plays, including Cat on a Hot Tin Roof, Camino Real, and Sweet Bird of Youth.

“I wanted to honor the role that Merlo played in all of Williams’s best work—to give him the depth and complexity of a main character in a drama,” Castellani says. In the novel, he even writes in a part for Merlo in a Visconti film. “None of that ever happened,” Castellani acknowledges. “But it was a metaphor for his ambition and how he was struggling to find a place in Williams’s world.”

In many respects, Merlo was more than just a lover; he was the muse for The Rose Tattoo, which was dedicated to him—and arguably the muse for other Williams plays, as well. Castellani prefers to talk about the “alchemy” the two men had together, although he admits that “it is not quite that either.” He notes, “Williams wrote in his memoirs that Frank kept him ‘tied down to Earth,’ not only because he was the one booking all his trips, organizing his pills, and ironing all his shirts but because he was the rational one. Williams was the neurotic. Frank was always the one talking him down and telling him that he didn’t have the latest disease. Williams was a hypochondriac. ‘Ballast’ is another way to think of it. Williams needed that foundation to write his plays. Without Frank, he frequently went adrift.”

Castellani first wrote about Williams and Merlo in 1999, in a short story from his grad school days at Boston University, where he received an MFA in creative writing. (He also holds an MA in English literature from Tufts.) But the story didn’t work.

“At first, I thought I just needed to make it a better short story,” Castellani says. “And then, I thought, ‘This is bigger; it needs to be a novella.’ ” Not one to waste words, Castellani ended up repurposing the piece as a two-part play titled Call It Joy, which appears in its entirety in Leading Men. He wrote the play in Williams’s voice; it’s just one of several pieces of literary derring-do, or alt fiction, in this portrait of artists and the leading men in their lives who served as muses for Williams.

The bulk of the novel is told from Merlo’s point of view. He is in a hospital in Manhattan, dying, at a time when Williams avoided visiting him. At the suggestion of the other patients on the ward, Merlo tries to recall the best moments in his life with Williams. Castellani says one of his inspirations was the idea of what it would be like to wait on his deathbed for the love of his life to visit him one last time. The novel concludes with Merlo’s real last words, which he said to Williams when he finally came to the hospital: “I’m used to you.” To the very end, Castellani notes, Merlo wanted to keep Williams guessing.

Castellani’s gambit of writing in Williams’s voice seems to have worked—as evidenced by the fact that this is shaping up to be the 46-year-old author and teacher’s biggest book to date. He was awarded a Guggenheim Fellowship in 2014 to help him finish it. Three years later, Paul Slovak, executive editor at Viking, bought Leading Men with a six-figure preempt from agent Janet Silver with Aevitas Creative Management; it has an announced first printing of 50,000 copies.

This fall, Castellani, who is artistic director of creative writing center Grub Street and a teacher at Warren Wilson College in North Carolina, visited two fall regional trade shows: NEIBA and NCIBA. At publication, he will return to the West Coast and visit other parts of the country on tour.

Part of the reason that Leading Men is on track to be Castellani’s breakout book is the way he uses alternative history fiction to get at the emotional and psychological truth of his characters, and the way he uses it to restore Merlo to his rightful place in Williams’s life and work. Castellani writes under the principle that, though not everything in the book is true, it is all possible.

A missing week in 1953 in Williams’s memoirs gave Castellani permission to use a party thrown in Portofino, Italy, by Truman Capote to explore Merlo and Williams’s relationship. Castellani places fictional Swedish actress Anja Bloom (née Blomgren) at the party to be a confidant of Merlo and, later in the book, to bring the story into the 21st century. The author imagines Anja’s mother to be at the party as well; an epigraph to a Capote letter refers to a Swedish mother and daughter who shared a fisherman between them. The mother has one more appearance with her daughter, in a weird and terrifying scene with cannibalistic gypsy boys who attack them. Castellani calls it a “fun house mirror” version, with the genders switched, of Williams’s Gothic one-act Suddenly Last Summer, which was turned into a screenplay by Gore Vidal.

Castellani says that deciding who got to tell the story was difficult. “Ultimately, I chose to make Frank and Anja the only two point-of-view characters,” he notes. “The book belongs to the both of them—their friendship, their respective muselike roles—though Frank is at the heart of both story lines.” He ended up working through how to tell the story by writing The Art of Perspective, which was published in Graywolf’s Art Of series.

Castellani makes a point of writing every morning. “If you write 300–500 words a day, they add up,” he says. “A lot of writers tell me that they’ve been so distracted since Trump got elected, but I’ve had the opposite experience. Writing this book was a refuge from the nightmare around me. I wanted to be in 1953 Italy; I wanted to be in Provincetown with Anja. Trump is already doing so much damage; I’m not going to let him take away my artistic life, too.”

Castellani is already well into his next project, which he says is “far from anything I’ve ever done.” He adds, “It’s based on a series of murders that have occurred around the U.S. over the last 20 years.” Let’s hope it doesn’t take another two decades to come to fruition.