It took Dr. Edward Taylor’s inside perceptions to say, on publication: “It is not merely an American book, but a California book. We do not mean merely that it is a book written in California by a Californian, but that it is distinctively and peculiarly Californian, for not only are its illustrations drawn from this coast, but the freshness of its views bespeak the novel and suggestive circumstances that have been presented in California.”
That is from Charles Albro Barker’s Henry George, still a useful biography. Barker points out, by the way, that the notion of a “single tax” on land barely appears in Progress and Poverty, as at that time George was more focused on land nationalization. The single tax idea became more prominent a bit later in the 1880s.