Book reader that reconstructs a book as x -> f -> f(x): the problem it addresses, the author's central answer, and how that answer changes judgment or action. USE WHEN the user gives a book title, PDF, excerpt, or asks 拆书, 分析这本书, 这本书在讲什么, 压缩一本书, or book. Defaults to a saved org note. NOT FOR chapter summaries, framework audits, papers, single-idea deep dives, or field ranking.