This document provides guidance on writing a reaction paper, which analyzes a piece by summarizing it, evaluating its strengths and weaknesses, and sharing personal reactions. It outlines a 5-paragraph structure including an introduction, 3 body paragraphs with supporting details, and a conclusion. The document contrasts reaction papers with diaries, noting reaction papers are more formal and aim to enlighten others rather than just the author. It provides questions to consider for each section and examples of modern iterations of reaction papers like reviews.