With its small plates and endless assortment of dishes, dim sum is an increasingly popular way to do brunch. For those new to this fun feast, or regulars looking to try a different dish, ''Dim Sum'' is the ultimate guidebook to this traditional Chinese meal. Perfect for popping into a purse or pocket, this handy guide identifies the 50 most popular dim sum dishes with full-color photographs, short descriptions of the ingredients, the names of the dishes in English and Cantonese, and how to pronounce them. As the carts roll by, a quick glance at the book will tell a jean gow choy bang (chive dumpling) from mong gwor bo deen (mango pudding), and demystify the contents of that bamboo steamer. With tips on restaurant etiquette and how-tos for everything from refilling the teapot to handling chopsticks, ''Dim Sum'' is yum yum for everyone.