From software design and specification to the social impact of technology, few software engineers have had the insight -- or the impact -- of David L. Parnas. Now, two leaders of the software engineering community have selected, annotated, and brought together 30 of Parnas' best papers: a lifetime of best practices that will be invaluable to every software practitioner -- and anyone who cares about the deeper meaning of information technology. Every article in this collection addresses a key problem in software development -- and presents insights that are as valuable now as when Parnas first shared them.