The Great Influenza
By John M Barry. I've been reading this, and it's really good. It explains things about viruses in general, and influenza in particular that I hadn't known before. It explains how viruses can acquire characteristics from other viruses, and how an initially weak virus, can increase in infectiousness and deadliness. How the "cytokine storm" is not a new thing, it happened 100 years ago. It explains "long Covid", because flu can do the same thing.
Covid-19 looks bad - but actually, we've dodged a bullet. Coronaviruses don't mutate as rapidly as influenza. Influenza is more like a swarm of similar viruses, of which a large percentage can't infect, but those that can, evolve rapidly.
Also, the symptoms, including anosmia, can be the same as for flu. And flu can be a bigger killer than Covid.
Spoiler - 50 million died, but eventually the pandemic ended.