Fred Waitzkin’s latest novel began with a phone call.

Mr. Waitzkin, Chilmark resident and author of Searching for Bobby Fischer and The Last Marlin, among other books, had lost two friends to age. As he dwelled on the past and last moments, he decided to place a call to one of his oldest friends, Ralph Silverman, a high school classmate.

Although Mr. Silverman now lived in a small apartment in Fort Lauderdale, he had spent nearly two decades homeless in South Florida. Mr. Waitzkin knew about that stage in his friend’s life, but during those years the two had talked rarely. It was only on the phone together, old age setting in, that Mr. Silverman told Mr. Waitzkin the full story of those 20 years.

“I hadn’t spoken to him for a while, and I called him up on the phone, and we started to chat, and I asked him about this period of time he sort of dropped out, dropped off the face of the world,” Mr. Waitzkin said. “And he told me the story, and it just knocked me out.”

That story forms the heart of Mr. Waitzkin’s new novel, Anything Is Good.

“One phone call turned into probably scores of phone calls and then that’s when I had the book,” Mr. Waitzkin said.

Anything Is Good pivots between the perspectives of Mr. Waitzkin and Mr. Silverman. As a young man, Mr. Waitzkin romanticized homeless life, infatuated with the tell-all stories of Jack Kerouac and George Orwell.

But when Mr. Silverman falls into real homelessness, his experience brings Mr. Waitzkin’s fantasy into stark relief: that life is dangerous and often debasing. Its pleasures, if any, are not adventuresome or outlandish: they are simple moments of conversation, romance and personal freedom.

Although Mr. Waitzkin calls the book a novel, elements are taken from real life, including his youthful romanticizing of homelessness, an experience he now shakes his head at.

“I would sometimes spend the night in Washington Square Park, pretending to be homeless, and then running home and trying to scratch out notes, pretentious notes, about what it was like to be homeless,” Mr. Waitzkin said, reflecting on his early ambitions.

“When my friend actually became homeless, at first... it felt like he was stealing my material,” Mr. Waitzkin said. “But that’s ridiculous, because he really was homeless. I didn’t really understand that at first. I thought that this was just something he was trying on because it was such a great idea.”

Decades later, after spending hours in conversation with Mr. Silverman and even more time researching homelessness, Mr. Waitzkin said he felt he could write the story with more depth and reality, rather than as an adventure tale.

As he wrote, the book’s political gravitas became clear to him, he said.

“I didn’t write the book because it was timely, but I realized when I was writing the book that it was timely,” Mr. Waitzkin said. “My hometown is Manhattan and from what I understand there’s between 200,000 to 250,000 homeless people living in Manhattan today, amidst the eight half million people that are normally living there.”

For years, Mr. Waitzkin worked as a journalist, an experience that made him nervous about showing his writing to his subject, he said. But when the book arrived as a galley proof, he sent a copy to Mr. Silverman.

“Ralph loved the book,” Mr. Waitzkin said.

It was a great relief.