In 1976, Hanff got a job to write copy for a book of photographs of New York City. Beginning her research, she made a list of "Must See" sights, and realized that she'd missed most of them! She'd never been to the Statue of Liberty, or Wall Street, or the Stock Exchange. She'd been to the Cloisters once, many years before, never toured Rockefeller Center, never been to Grant's Tomb. So she enlisted her friend, Patsy Gibbs, and the two of them spent two months doing the things tourists do in New York City.
However, this is not a guidebook. It's written from the point of view of a longtime resident, and is as much about the people as the sights. Hanff minces no words when she disapproves of something (the loss of Central Park land for additions to the Metropolitan Museum, the soullessness of theTrump Tower), but you'll be in no doubt about the things she loves, either (the Statue of Liberty, the skyline and so much else). The East Side/West Side split is analyzed and explained ("East Siders are conventional and proper, part of the Establishment and in awe of it -- which God knows, and God be thanked, West Siders are not."). She revels in the city's diversity ("And you won't believe it, but on Allen Street there's a Kosher Chinese restaurant where the Chinese waiters wear yarmulkas.") She acknowledges the bloody history behind the fortunes (Frick, Morgan, Rockefeller) that nevertheless contributed so much to the ordinary people of the city, those whom John D. Rockefeller III called "the many".
Times change and cities change, though, and it's amusing to read about the shocking "suggested contribution" at the Cloisters: $1.75. The Met and the Cloisters are now charging $15 (though one payment will get you in to both if you're crazy enough to try to see them on the same day), and the Museum of Modern Art wants $20 from you if you want to enter its lovely new building. The edition I read is, in fact, a later one, published in 1988, and Hanff notes a number of changes in several "P.S." chapters. (Sadly, Gibbs had died of breast cancer several years before this edition.)
Hanff admits it when she's wrong about something, too. She had gloomily predicted that damage to Central Park from a subway excavation would never be repaired. It was, with no scars.
Even if you can walk to Zabar's in your sleep, you'll find something you didn't know about NYC in Hanff's book.