I admit I was expecting a bit more footing around. The only places White actually describes walking are when he talks about Baudelaire's curious way of walking the pavements, and when he describes hunting for rough trade on the Ile de la Citee on nights that passed during his sojourn in Paris. Apart from that we are given more historical information than details about the actual appearance of the Parisian streets.
So the subtitle of the book is not quite accurate. More accurate would have been 'An American progressive's version of Paris' or some such. Which does not mean the book is not worth reading. It is. Just do not expect a tour guide or a dolorous account of slipping among the raindrops down dim cobbled streets around dinner time. (Which would have been preferable from my point of view.) This is a cultured American gentleman's version of Paris and it's worth a look even though the word "flaneur" tends to appear only occasionally, as the beginning of sections, being soon eclipsed by something of more pressing interest to the writer, such as Jazz Age performers and the current claimant for the Bourbon throne.