Architect and writer James Sanders's new book, "Celluloid Skyline: New York and the Movies," was exactly one week from going to press on Sept. 11. The terrorist attacks that forever changed the city also forced Sanders to make some hard decisions about the book, which explores the mythic New York City depicted in American films.

Sanders was traveling that morning, flying to Los Angeles to pose for the book jacket's author photograph on a Paramount Studios set that re-creates a New York street. Days later, when he returned to his TriBeCa loft just seven blocks from the World Trade Center site, he had "a panic thing," he recalls. Sanders wanted to postpone the book's publication, but his publisher, Knopf, and his agent convinced him otherwise.

"Their argument was that far from being the wrong time to bring it out, it was completely the right time to bring it out -- that what had just happened had, in this totally horrible, awful way, nonetheless powerfully reinforced what I was trying to argue: that cities exist in the imagination as well as physically," says Sanders.

"Cities have a very palpable hold on us, and I think what happened and . . . the huge outpouring of feeling that people had was because they felt it happened to a place that they knew, that they on some level had imaginatively inhabited for all their lives," he explains. "They may not really know it in a profound, interior way, but they have some real knowledge of the city through movies."

Knopf went ahead and published "Celluloid Skyline" last month. And while Sanders had hoped to revise what he describes as his "slightly flippant" treatment of such disaster movies as "Independence Day" and the 1998 "Godzilla," the only change in the book was the addition of a one-paragraph author's note. It suggests that the book "may in some way help to further an understanding of why the New York skyline -- in both image and reality -- has had such profound and personal meaning for people all around the world."

If you pause for a moment and think of your favorite New York movie scenes, you might understand what Sanders is getting at. Fred Astaire and Ginger Rogers gliding across the shiny floor of a sparkling rooftop nightclub. Dustin Hoffman's grimy Ratso stopped in the middle of an intersection, banging on a taxicab hood in "Midnight Cowboy." Or maybe Robert De Niro's Travis Bickle alone in his seedy apartment, rehearsing for confrontation in "Taxi Driver" -- "You talkin' to me?"

More than 100 years' worth of films set in New York, writes Sanders, have created a movie city "so dense in texture, so rich in memory and association and sense of place, that it forms an astonishing urban presence. . . . A great city is more than a geographic or economic entity: It is a distinct locus of image and style, memory and dreams. This is precisely what the New York of the movies offers."

Movie New York, writes Sanders, is more vivid than the real place could ever be. "Instantly memorable, visually stunning, it is a place built specifically for action, for drama, for adventure, a city of bright avenues and mysterious side streets, of soaring towers and intimate corners, all designed to heighten and accent the movement of its larger-than-life inhabitants."

Sanders, 46, was raised on the Upper East Side and first became entranced by New York movies as a child when his father, who abhorred Disney's family fare, took him to see black-and-white classics at the city's revival houses. His interest in architecture, too, was a gift from his father. The elder Sanders, an engineer, was fascinated by urban spaces. "Since I was about 17 or 18," says James, "dinner table conversation has been about cities and architecture and how to improve New York."

Sanders wrote his first proposal for "Celluloid Skyline" while a senior in college. "There were all these things that I wanted to say about cities, particularly about New York," he says. "All these films had sort of lodged themselves in the imaginations of people all around the world. . . I had this intuition that it might be a really interesting way . . . to talk about a lot of the things I wanted to say about cities. So in a way, my book's not about the movies at all; it's about cities."

Actually, "Celluloid Skyline" is about movies and cities, though Sanders has more to say about the latter. One of the book's most interesting segments relates how homesick screenwriters imported to Los Angeles from New York after the advent of sound created an "impossibly grand" version of the city they left behind. "The dream city was, in fact, the unlikely issue of both places, somehow joined together," writes Sanders. "Years later, a few of the writers came to realize it; as [screenwriter] Herman Mankiewicz himself was heard musing over a drink one day in the late 1940s at a midtown bar, 'Oh, to be back in Hollywood, wishing I was back in New York.' "

Much of the amply illustrated "Celluloid Skyline" is divided into studies of films that take place in different types of buildings. A chapter titled "Something Big" explores the skyscrapers and office buildings of such films as "The Apartment," "The Fountainhead," "Working Girl" and the Coen brothers' "The Hudsucker Proxy." The "Street Scene" chapter visits row houses, tenements and housing projects. The "Lofty Perches" chapter scales its penthouses, terraces, rooftops and elevated nightclubs, while "Dancing Lights" looks at cinematic versions of Broadway and Times Square. Later chapters deal with films shot on location by such New York mainstays as Woody Allen, Martin Scorsese and Sidney Lumet.

Throughout the book, Sanders comes off as someone with a lot of knowledge -- and strong opinions -- about architecture. His discussion of "Rear Window" leads him to conclude that director Alfred Hitchcock's understanding of architecture and cities was more sophisticated than that of leading architects of his time. Later, in his examination of "Three Days of the Condor," the author refers to the "soulless world" symbolized by the World Trade Center towers. "The Trade Center was not in its design a humane public place, a soulful place," Sanders says now, adding that he never considered changing this section after Sept. 11. "It was a cold, anonymous, largely soulless environment."

As an architect, Sanders worked for various civic organizations and city agencies (including the city's Parks Council, the Landmarks Preservation Commission and the Port Authority of New York and New Jersey) before founding James Sanders & Associates, which he runs out of his TriBeCa loft. He has contributed articles to various newspapers and magazines, and wrote with Ric Burns the recent seven-part PBS series "New York: A Documentary Film."

Once he started "Celluloid Skyline," he noticed a troubling discrepancy. "When I wrote about the city parts, the architecture parts, there was this tone of authority that was unmistakable. When I wrote about the film parts, it was completely thin," he says. "So I just had to teach myself about the movies until there was an even tone."

He read books about films and filmmaking, and went to Hollywood to meet with art directors, production designers and the photographers who shoot standing sets. "I didn't want to be one of those people -- and I associate this with New York critics -- who just sit in movie theaters and watch movies and think they know about movies," he says. "The architect in me just had to go and find out how this was done."

In a protracted section on the 1949 film "The Heiress," Sanders examines how director William Wyler positioned characters in various rooms of a set replicating an early-19th-century row house; where they stood underscored the developments of the plot. This, says Sanders, is part of what sets "Celluloid Skyline" apart from other movie books, which have rarely focused on film sets. "When they did look at them, they looked at them absolutely on the model of the way literary criticism deals with settings in books and also to a lesser degree, plays -- which is, they're to be looked at for their symbolic quality," he says.

"But almost never, as far as I knew, had anybody ever looked at film settings spatially. It's not enough to say where it took place. What happened? How did they use the environments of spaces that they're in? How do they move through those spaces and how do they understand those spaces? . . . How were the directors using that spatial movement to say something rich and interesting? First you say, 'How is the space helping the movie?' Then you flip it around and say, 'How does the movie teach us, in turn, something about the space that we didn't see before?' "

These are crucial points, says the author, with a combination of earnestness and pomposity that is not uncommon among this city's downtown intelligentsia. But many of the book's reviews, while positive, have not been as insightful as Sanders would like. "A lot of reviewers were not able to get past the most obvious things about it," he says. "It was almost like all they did was basically read the captions.

"The other thing that people haven't -- for my taste -- sufficiently appreciated is that this book has nothing to do with nostalgia. It's a book about the city of the future. For me, it's a primer of what makes cities work in a really profound and important way," he says.

"There's a city embedded in that book. . . . I think that city should be one of the things that we look at and think about as we move forward in building real cities," he says. "Six months ago, the idea of needing to build a new city was a little bit of an abstract idea. What I could never have known is how pressing that need would be."

"Cities have a very palpable hold on us," says James Sanders, author of "Celluloid Skyline."A sense of place: Melanie Griffith in "Working Girl"; Fred Astaire and Ginger Rogers, below, gliding across the dance floor of a nightclub in "Swing Time."Sanders's book touches upon such films as (ascending from above) "Taxi Driver," with Robert De Niro; "Rear Window," with Grace Kelly and James Stewart; and "The Apartment," with Jack Lemmon and Shirley MacLaine.