For 35 years, librarians sent puzzles they could not solve locally to The Exchange (a column for reference librarians appearing in the official journal of the Reference and User Services Division of the ALA). Other readers often furnished the answers - sometimes years or even decades later! Puzzles and Essays from The Exchange organises those fascinating questions and answers into a reader-friendly reference format, embellished with essays that appeared in the column over the last fifteen years of its publication.