The classic Negroni -- a 1:1:1 mixture of gin, Campari, and sweet vermouth, with an orange twist -- is the perfect blend of the bitter, the sweet, and the botanical. It's replaced the martini as my favorite gin-based cocktail.
The first part of this book is the most enjoyable: it's a fascinating account of the real Count Negroni, a former cowpuncher and rodeo rider (and inveterate gambler), who, after some decades in America, returned home to Florence. It was there, around 1919, that he asked his bartender to substitute gin for the club soda in his Americano, creating "Italy's one contribution to global cocktail culture," as one writer has put it. Besides the classic recipe, Regan also looks at the Negroni's ancestors: the Americano, the Torino-Milano, and the Milano-Torino.
The second part is a long list of recipes for increasingly outré Negroni variants, calling for everything from mezcal and cachaça to peach liqueur, coffee beans, and roasted figs. They're interesting to contemplate; I just wouldn't want to drink one.