Tall and slim, 21-year-old Missourian Clifford Johnson was on a first date at the Cocoanut Grove in Boston in 1942 when fire raged through the famous watering hole. Johnson was swept out the door by the panicked crowd, but lost his grip on the hand of his date, Estelle Balkan.

Four times the young Coast Guardsman plunged back inside, hoping in vain to rescue her before his luck ran out and he emerged a ball of flame, so seriously burned doctors expected him to die within hours.

But he didn’t, and Johnson’s 21 months of painful treatment bring a true human story to the hundreds killed in that blaze, detailed in John C. Esposito’s book “Fire in the Grove” (Da Capo Press, $24).

Johnson’s isn’t the only story in the well-researched volume, though it is perhaps the most painful to read about.

Esposito also probes the causes of the fire; tells how it swept along fabric-covered walls and ceilings; points out the locked or blocked escape doors and the failures of city officials to enforce safety codes and details the follow-up investigations.

Among those jammed into the packed club that night was Western movie star Buck Jones, who had wanted to rest after a day full of meetings but was talked into making the appearance.

Most of the 30 people with Jones died on the spot. The star was found alive but died two days later of burns and smoke inhalation.

The conflagration began in an artificial palm tree in a basement lounge at 10:15 p.m., Esposito reports, raging up a flight of stairs and sweeping through the several rooms in the club in just eight minutes.

The cause? Probably a young worker who lit a match to find a light bulb that had gone out. A fire inspector later testified that he had tested the tree with a match and it wouldn’t burn for him.

It turns out that some exit doors had been locked, another was blocked by a coatroom and the main entrance was a revolving door that jammed as the fleeing crowd pressed into it.

In the end, at least 490 people died in the blaze. And 14 years later, Johnson was driving home from work when his car skidded, overturned and burst into flames. This time, he burned to death.