I recently visited NYC for the first time. I took only three books about that city with me: this guide, the "Top 10 New York" guide, and "The Metropolitan Museum of Art Guide". I must say that the "Lonely planet NYC Guide" was not my favourite, though.
Truth to be told, this guide has a lot of useful information, and that proved helpful in some cases. What is more, it has some interesting planned walking tours that I liked, and good sections with data about the city and its history.
On the other hand, this guide doesn't have too many photos in color, and it includes some maps that are not specially good, particularly if you compare them with the spectacular maps of the "Top 10 New York" guide. Furthermore, it is big enough to be heavy, something that you will not appreciate if you have to carry it with you the whole day.
On the whole, I can say that I liked this guide, but I recommend it only as a complement to the "Top 10 New York" guide, or another small guide like that, the kind of guide that you can carry with you while you leave the "Lonely planet NYC Guide" in your hotel room to check at night if needed. Enjoy your trip :)