Imagine writing a novel, but never being able to read it. In the summer of 2005, CBC News interviewed Toronto author Howard Engel about his latest Benny Cooperman detective novel, Memory Book. Five years before its release, Engel — a veteran CBC producer — suddenly found himself unable to read. A stroke was to blame. And though Engel could still write perfectly, the ability to recognize individual letters, never mind whole words, was lost to him.

There's a name for Engel's problem: alexia sine agraphia. It's a rare and mysterious neurological condition. Years ago, as Engel was rehabilitating in a Toronto hospital, it seemed to him that this was the perfect case for Oliver Sacks.

Sacks, the famed neurologist and author, died this week of cancer. His books, detailing his medical case histories, revealed both the wonders of the mind and the human spirit. The patients featured in his stories often became friends, Engel included. Sacks featured the Toronto author's experience in his New Yorker article, "A Man of Letters," a piece which also appeared in his 2010 book The Mind's Eye. It was Engel who initially reached out to Sacks, sending what's referred to in the article's charming intro as a "strange letter."

"I was a great admirer of his writing," Engel tells CBC Arts, "how he was able to catch an audience with a rather novel beginning in a piece. You know, 'The Man Who Did This, or Did That,'" Engel says, referencing the title of Sacks' famous book The Man Who Mistook His Wife for a Hat. After suffering the stroke, Engel couldn't help think his experience was like something out of a Sacks story. "It sounded so much like what he'd been writing about. And I was, in fact, a 'writer who had forgotten how to read.'" (The title of Engel's own book about his condition, The Man Who Forgot to Read, was selected by his publisher as something of an homage to Sacks.)

When Sacks responded to Engel's letter, he asked to quote him in that aforementioned New Yorker piece. But he also invited him to visit, and with a trip to New York already planned, they set an appointment to meet at his Greenwich Village office.

"I was surprised how much like Robin Williams he was, even in small gestures," Engel says of his first impression. (Williams played Sacks in the 1990 film Awakenings.) "It was very clinical to begin with. He was behind his desk and I was in the patent's chair, and behind me was a chalkboard with my name printed on it — so he would never be at a loss as to whom he was talking," he recalls.

"He challenged me at that time to finish my book," Engel says of The Man Who Forgot to Read, "and said that he would write an afterword to the book if I finished it." Sacks kept his promise, writing that the book is "a testament to the resilience and creative adaptation of one man and his brain." And from that first meeting, a friendship developed, as the authors visited one another at home in Toronto or New York.

Engel published his story in his own words, but the experience of being one of Sacks' case histories was a special one. "I don't know anyone who wasn't charmed by Oliver, and opened up to him," he says of being a subject. "He was very open and witty and funny. And generous."

"I'll miss him," Engel says. "I'll miss his humour, I'll miss his humanity. I think he was the best friend the brain ever had."