"Getting Things Done: The Art of Stress-Free Productivity" by David Allen is a comprehensive guide to managing tasks and projects efficiently. Here are the key points:

1. Capture: Collect all tasks, ideas, and commitments in a trusted system outside your mind.
2. Clarify: Process what each item means and decide on the next action steps.
3. Organize: Categorize tasks and projects into appropriate lists (e.g., Next Actions, Projects, Waiting For).
4. Reflect: Regularly review your lists to keep track of progress and make necessary adjustments.
5. Engage: Use your system to decide what to work on at any given moment based on context, time, energy, and priorities.

Allen emphasizes the importance of having a clear mind to focus on tasks effectively and reduce stress. The book provides practical tools and techniques to help you implement the GTD system and achieve greater productivity and peace of mind.