One of the major documents of modern European civilization, Robert Burton's astounding compendium, a survey of melancholy in all its myriad forms, has invited nothing but superlatives since its publication in the seventeenth century. Lewellyn Powys called it ''the greatest work of prose of the greatest period of English prose-writing,'' while the celebrated surgeon William Osler declared it the greatest of medical treatises. And Dr. Johnson, Boswell reports, said it was the only book that he rose early in the morning to read with pleasure. In this surprisingly compact and elegant new edition, Burton's spectacular verbal labyrinth is sure to delight, instruct, and divert today's readers as much as it has those of the past four centuries.