Crosby's "America's forgotten pandemic" is probably still one of the best academic or popular books on the outbreak.

The book is not heavy on theory, though Crosby isn't one to usually get too bogged down in any of his other seminal works. Despite the book generally being US focused it doesn't present something of a global perspective.

Overall it's aged fairly well, though casualty statistics have definitely been revised upward since Crosby wrote-- though I think he anticipated as much as the sources regarding the dead are sometimes a bit spotty.