Atomic Habits — James Clear (2018)

James Clear's Atomic Habits has sold over 15 million copies in six years, making it one of the best-selling self-help books of all time. Its central insight — that 1% improvements compound dramatically over time, and that behaviour change is most effective when driven by identity rather than goals — provides one of the most actionable frameworks for habit formation available. It distills decades of behavioural science into immediately applicable strategies.