In his essay, We'll Map Manhattan (the link should work even without registration), Cohen explains that he wants to create a "literary map" of Manhattan, which will list the homes and other important locations associated with characters from literary works.
I'm personally fascinated and delighted by this project. On a self-serving note, I'm scouring my own minor bibliography to see what Manhattan locations my own characters used. On the other hand, I grew up in New York City and love reading about the city and its history, so such a project would naturally appeal to me. But on a broader scale, what delights me about this whole project is the concept of reader identification.
Lawrence Block discusses this concept in his essay "Mirror, Mirror on the Page," which can be found in his book Spider, Spin Me a Web: Lawrence Block on Writing Fiction. A bookstore proprietor recommended a book to him once set in Santa Barbara, with the promise that it was filled with local color. Block discovered that the book's story could have been set anywhere, but by identifying specific parts of Santa Barbara, the writer had managed to appeal to people from that city.
I think we all experience that in some way, and not just in books. I grew up in Forest Hills, Queens, and am bizzarely proud of the fact that so did Peter Parker (AKA Spider-Man). When gnomi and I went to see the first Spider-Man movie here in the Boston area, I jumped out of my seat when I saw Parker running through the intersection of Austin Street and Ascan Avenue, three blocks from where I grew up (and where, coincidentally, the first comic book store I patronized was located). I've often joked with people by saying that we used to see Spider-Man swinging through the streets on his way home from Manhattan.
Why does this identification with place resonante so vividly? Block suggests a few explanations, but the one that resonates most with me is this one: "...the presence of real parts of our own real world helps convince us that the writer knows what he's talking about... The more I can accept the idea that the author knows whereof he writes, the easier it is for me to believe further that the fictional story he's relating is true -- and it is upon this voluntary suspension of disbelief that fiction depends for much of its power to move us."