"Most textbooks are unreadable, dense, and boring," Downey told me, "1,000-page books with no personality." There were plenty of textbooks available for his introductory course on the Java programming language, for example, but each chapter was typically fifty pages or more, and many students couldn't slog through the reading. Worse, the material was poorly organized: the first few chapters were easy, but "then the trapdoor opened, and students fell through the floor."89