PARIS — It became the indispensable book of the pandemic, its French author revealing how society’s weaknesses and human frailties gave way to disaster. As the coronavirus tore through France, intellectuals, historians and journalists cracked open their old copies in search of eternal truths in an unsettling time.

No, it was not Albert Camus’s “The Plague.’’ It was “Strange Defeat’’ by Marc Bloch.

In the country that gave the world the classic novel, it is “Strange Defeat’’ — a scholarly dissection about the fall of France in 1940 not widely known even inside the country — that has instead become the reference to understand what went wrong this time.

Why did France record one of the world’s highest Covid-19 death tolls and mortality rates? Why is it expected to suffer a catastrophic drop of 11 percent in its gross domestic product?

Some French have sought clues in “Strange Defeat,’’ which described a country that, in 1940, believed it had the best army in the world but that was trounced by Hitler’s forces in six short weeks.

Bloch, a historian and army officer, wrote the book in the months following France’s collapse, explaining how an ossified bureaucracy and an out-of-touch elite had left his country without the proper defenses and without the critical capacity to adapt to a rapidly changing situation on the ground.

To some readers, the parallels to 2020 cannot be ignored.