Tomorrow sees the reissue of what is surely one of the best non-fiction books ever written: The Death of a President, by the historian and foreign correspondent William Manchester. (It's also being released, for the first time, in ebook and audiobook versions.) It is an utterly extraordinary thing: a 700-page analysis, in microscopic detail, of the events of November 20-25, half a century ago this year, based on a thousand interviews, including with Jacqueline Kennedy, Robert Kennedy, Lyndon Johnson, and Lee Harvey Oswald's mother and brother.

To give one example: it includes a 14-page account of a single minute, 12.21pm, eight minutes before the presidential motorcade turned into Dealey Plaza. The Kennedy family initially authorised the project, but then Jackie launched a legal fight to halt it, delaying publication until 1967 and all but destroying Manchester physically and psychologically in the process.

I got hold of a battered second-hand copy earlier this year. Reading it essentially took over my life for a couple of weeks: that's how emotionally all-encompassing the experience is. Obviously, I'm not going to try to do it justice in a blog post. You should really just read it.

I'll say this, though: when you analyse an event in as much painstaking detail as Manchester did, you unearth some very strange details. When you think about it, that's inevitable: freeze-frame any single moment in history, especially one which sent such shockwaves round the world, then subject it to sufficient examination, and you'll find people doing all kinds of inexplicable things which seem deceptively meaningful in hindsight. Some of these, of course, helped fuel decades of conspiracy theories. What were those two men doing behind that picket fence on the grassy knoll, and who was that man opening a large black umbrella on a hot Dallas day? Other details are just plain creepy – and one of the creepiest occurs on page 178 of my edition of Manchester's book.

The scene is Parkland Memorial Hospital, where the dying Kennedy was rushed within minutes of the shooting. (The new movie Parkland, starring Billy Bob Thornton and Paul Giamatti, takes the hospital as its focus.) Over the following few hours, as news of the assassination began to envelop the planet, the switchboard room at Parkland started receiving hundreds of crank calls. The Army Signal Corps had commandeered Parkland's outgoing lines, but that still left the incoming ones to be handled by the regular switchboard operators, who were soon overwhelmed. Manchester writes:

Already UPI bulletins were stimulating cranks all over the world. In the next two hours one girl, Phyllis Bartlett, would log conversations with England, Canada, Australia, Venezuela, France, and Mexico. She wrote: "Every call coming in long distance is urgent and everyone seems to have a title that demands priority." Some of the titles were legitimate. Most weren't. Genuine insiders went through Signals, as Ethel Kennedy had. The bulk of the direct-dial long-distance calls came from the curious, the disturbed, the downright demented. A woman in Toledo identified herself as 'The Underground'; she asserted that she had occult powers which would keep Kennedy alive. A man said, 'You nigger lovers, you killed our president.' Another man threatened an operator: 'I know who you are, and you'd better be careful when you start your car.' Most disquieting was a young boy who called three times, talking to a different operator each time. His approach never varied. 'I want to talk to my Daddy,' he would begin plaintively. Asked who his father was, he would say, 'My Daddy – President Kennedy.' Then he would giggle and ring off.

Let's just say I found it hard to get to sleep the evening I read that.