Sad news, this morning: the author Daniel Keyes has died, aged 86, his US publisher Tor has announced.

Keyes wrote other books too, but I and millions of others, knew him for one in particular: Flowers for Algernon. It's the story of Charlie Gordon, a cleaner who has an IQ of 68, but who "reely wantd to lern I wantid it more even then pepul who are smarter even then me … all my life I wantid to be smart and not dumb".

University researchers perform an experiment on Charlie, turning him into a genius, after their successful experiments on the lab mouse Algernon. "You know Charlie we are not shure how this experamint will werk on pepul because we onley tried it up to now on animils." But Algernon's new intelligence begins to fade, and he dies, and Charlie realises that his genius, too, is destined to leave him.

The book is written as a series of diary entries by Charlie, with his spelling and grammar and clarity of thought improving – "This is beauty, love, and truth all rolled into one. This is joy" – and then falling away. "Please … please … dont let me forget how to reed and rite … "

The New York Times piece about Keyes' death reveals that the premise "struck him while he waited for an elevated train to take him from Brooklyn to New York University in 1945". Keyes wrote, in his 1999 memoir, "I thought: My education is driving a wedge between me and the people I love. And then I wondered: What would happen if it were possible to increase a person's intelligence?"

Keyes first wrote about Charlie in a short story, which won him the Hugo Award in 1960, going on to expand it into a novel, which won a Nebula in 1966. The tale also won an Oscar, as the 1968 film Charly.

I think Flowers for Algernon is heartbreaking, and utterly, completely brilliant. My copy has an introduction from Jon Courtenay Grimwood in which he calls the book a "work of genius". High praise indeed, but I think he's right. Flowers for Algernon is, as Grimwood puts it, "eerily perfect". It's one of those books which feels destined to have been written, somehow – the idea behind it is just so perfect, so horribly disturbing.

Others clearly agree: the novel has sold more than five million copies, and has never been out of print since its original publication, according to Keyes' website.

"We were, of course, greatly saddened by the news but there's a comfort in Daniel Keyes having had a long life and that he left us with a great legacy; a wonderful, heartbreaking book," said Simon Spanton, at Keyes' UK publisher Gollancz. "In its pitilessly tight focus and tragic story arc, delivered in a first-person narrative whose very nature cuts to the core of what is gained and then lost, it is for me the most heartbreaking book in the genre."

"PS please if you get a chanse put some flowrs on Algernons grave in the bak yard." RIP, Mr Keyes. And thank you.

• Daniel Keyes obituary