Before it was a comedy on HBO, Sex and the City was a novel written by Candace Bushnell. First published in 1997 by Warner Books, SATC follows the lives of 30-somethings living in New York City.
The book contains many of the main characters from the show, including Carrie, Samantha, Miranda, Mr. Big, and a few others. It does differ from the show in many ways. It doesn't simply follow the paths of 4 women talking about sex, and the book isn't even narrated by Carrie, but rather by some woman (presumably the author).
The book is entertaining, especially if you enjoy the television show. It even has chapters centered around types of men in NYC. It is clever, perhaps moreso than the show, and face paced. It is written almost like a documentary of the "Age of Un-Innocense". However, as my boyfriend always says, it might not be the best read for men; it may contain things you've never wanted to know about women. (Not all women mind you, just these women, but there are traits in characters that any female could relate to.)
Candance Bushnell has also written the book "Four Blondes."