The 100 best moderately difficult nonfiction books

The book is a cornerstone of biology, history of science and Victorian studies, assigned across disciplines worldwide. It is among the most widely taught scientific texts ever written.

Selections centred on On the Origin of Species — among the most taught and cited works in the history of science.

Orientalism is required reading in postcolonial studies, comparative literature, cultural studies, history, and Middle Eastern studies curricula worldwide. It appears on thousands of university syllabi across disciplines and is considered foundational to the field of postcolonial criticism. No academic in the humanities can avoid engagement with Said's argument, making it one of the most canonical critical texts of the late 20th century.

Freud's founding work of psychoanalysis is taught across psychology, literary theory, philosophy and the history of ideas, and is a standard text in courses on modernism. Few works published around 1900 hold a comparable place across so many disciplines.

The Declaration and the Constitution are taught in American schools from primary grades through law school and appear in civics and history courses everywhere. They are among the most reprinted and studied texts in the English-speaking world.

Plato's Phaedrus is a foundational text in Western philosophy, taught in virtually every philosophy curriculum worldwide from undergraduate ethics to graduate seminars on rhetoric and metaphysics. The dialogue has maintained continuous scholarly presence for 2,400 years, appearing on Open Syllabus lists for philosophy, rhetoric, and classical studies courses across hundreds of institutions. Its Wikipedia article spans over 50 languages for the work as a whole.

The Preface to Lyrical Ballads is the founding manifesto of English Romanticism and appears on every university syllabus in Romantic literature, literary theory, and criticism courses. It is required reading in virtually all English literature programs and is cited as the document that defined the terms of English poetry for the 19th century. Its presence in literary education is as reliable as any text in the tradition.

Three Essays on the Theory of Sexuality is a foundational text in psychology, psychoanalysis, sexuality studies, and cultural theory curricula worldwide. Listed among Le Monde's 100 Books of the Century (1999), the Open Syllabus Top 500 in Literature, and available on Wikipedia in 20 languages. Taught in psychology, philosophy, literature, gender studies, and history of science courses, it is considered inescapable for anyone studying psychoanalysis or the history of sexuality.

The foundational text of American constitutional theory, cited by the Supreme Court.

The Enquiry is a staple of introductory philosophy and early-modern courses worldwide, usually paired with Descartes and Kant. It sits among the core texts of the empiricist tradition.