Every skill in this book ends with the mistakes that make smart people produce weak work. Collected, they read as one long answer to a single question: what does experience actually know? Part I is the craft of professional work in full — PRDs to postmortems, incident reviews to go-to-market plans, meeting notes to board updates — the fifty production-grade chapters of an open library used across Claude, ChatGPT, Gemini, and Cursor, each with its quality checklist, scoring rubric, and anti-patterns. Part II is the Anti-Pattern Almanac: 2,563 rules of professional judgment extracted from all 515 skills — the "do not" knowledge that normally takes a career to collect. Written to instruct AI; readable as a book by humans. Use it to brief an assistant, to review a colleague's draft, or to check your own work before someone else does. The digital edition is free forever at the pm-claude-skills open library — this one is for your desk.