A decade ago, Andrew Ross Sorkin, a journalist, TV anchor and co-creator of the show Billions, started obsessively studying the 1929 stock market crash. Now he has finally published a book about that event — with clever timing. For with tech stocks having gyrated wildly this week, there is intensifying debate about whether we have just witnessed a bubble linked to hype about artificial intelligence, which is now set to burst.

Invoking history is currently all the rage, whether your year of choice is 1929, 2000 or 2008. “I got lucky”, Sorkin told me during a debate this week, with a chuckle.

So what lessons can investors learn? The most significant one here is that manias are never “just” about stock market swings, however eye-catching — they are also about excess leverage, ample liquidity and investor lunacy.