Also, the book explains how huge numbers of deaths were caused by politicians and bureaucrats. The political machine in one city (Philadelphia, I think) refused to shut down a popular parade, as urged by the health authorities, to stop the spread of the flu. Lots of people needlessly got infected and died. The military packed excessive numbers of WWI recruits into camps designed for a fraction of the number of people, also against the advice of doctors; huge numbers of healthy young men caught the flu and died.
And the scientific detective story of how researchers tried to find a cure for the flu was very interesting, with ongoing controversy over what the infectious agent was (virus? bacteria?). We know the answer today, but it wasn't so clear back then.
It's a very good read on many levels.
Here's a link to the book on Amazon: https://www.amazon.com/dp/0143036491
The book does a great job of expressing the history of medicine leading up to the 1918 Spanish Flu.
But above all the book goes into detailed recollection on the arrogance of leadership in the face of this deadly disease. From politicians listing it as merely a regular flu, to military generals choosing not to quarantine troops... leading to massive casualties and the spread of the disease. All leading up to a realization of severity, when proper measures are taken.
I believe a newer print also has a note about Swine Flu, my copy is fairly old and does not include this.