With 20 million copies of her books in print in 18 languages, Barbara Delinsky is no stranger to bestseller lists. Still, landing a new book, Coast Road, in the top 15 -- the only newcomer on this week's hardcover lists -- is a sweet victory. A $225,000 marketing campaign backs the latest work by this popular author of contemporary women's fiction; three printings bring the in-print total to 180,000. Movie rights to the Simon &Schuster novel have been sold to TriStar.