Clean Code: A Handbook of Agile Software Craftsmanship

Uncle Bob's argument is that code is read far more often than it is written, so readability is not a courtesy but the primary engineering constraint. The book moves from the small to the large: naming, functions that do one thing, comments as a failure of expression, formatting, error handling, boundaries, unit tests, classes, and finally systems. Roughly half the volume is extended case studies where Martin refactors real code in front of the reader, showing the intermediate ugly states rather than only the polished result. The advice is opinionated and occasionally dogmatic — the very short function rule draws the most argument — but the underlying discipline of leaving code cleaner than you found it has become industry vocabulary.