Simplify the following text for a Grade 10 native English-speaking person.
Original: Lisa Birnbach 's humorous `` guides '' , The Official Preppy Handbook and its sequel True Prep : Itâ s a Whole New Old World , say Lilly Pulitzer clothing is a must-have item for `` preppy '' women .
Simplified: In 1980 , Lisa Birnbach 's bestselling tongue-in-cheek `` guide , '' The Official Preppy Handbook , featured a golf skirt and `` Lilly beach dress '' as must-have items for `` preppy '' women . Arguably , Lilly Pulitzer 's clothing was at the height of its original popularity in the early 1980s .