Carrie Bradshaw may know good sex, but Cindy Chupack -- an Emmy-winning writer and producer of ''Sex and the City'' -- is the woman responsible for many of her on-screen bons mots. Chupack's wit is apparent in this collection of relationship essays, The Between Boyfriends Book, each cleverly titled with mock definitions of dating terms (e.g., ''CUPIDITY: The faulty logic that leads a well-meaning but clueless third party to believe that two random singles are perfect for each other''). And her breezy observations (sometimes too breezy; many of the essays originally ran in Glamour) are as hilarious as they are true. Chupack on dating married men: ''You realize...you are not, in fact, Julia Roberts. At best you're one of the Arquette sisters -- in for an act or two, a catalyst for someone else's story.''