Do not pick up this book expecting to find a written version of the show.
Yes, the show was based on it, but the style and substance is quite different. The book is much more random and wandering, only loosely following Carrie and Mr Big. From start to finish it is a collection of snippets; moments in new york relationships and conversations discussing why they are the way they are. It is much more cynical and not nearly as pretty as the show.
The TV series has much more clearly defined characters who are also much more likeable and easy to identify with. It reveals much more of their personalities and lives, and contructs a complete narrative around the main characters. The show could not have reached such a wide audience and lasted 6 seasons if it had imitated the book perfectly.