A quick read (listen) that I enjoyed was The Power of Less by Leo Babauta. It was quite similar to The 4-Hour Workweek and Getting Things Done in its essence, though it was a bit less extreme and less detailed in its methodologies (this was both good and bad). I honestly found the book a bit too general/high-level as it tried to cover a very wide range of topics. The best parts were when the author wrote of his own personal experience and used specific details of life changes he made and how he went about that.
The takeaways I liked best were applying constraints/limits to all aspects of life and choosing the 1-3 big, challenging tasks each day that are required to move towards one's long-term goals, rather than simply doing what's easy and taking care of low-hanging fruit.
Ch. 1: Why less is better
Ch. 3: Choose the essential and simplify
Part 2: In practice
Ch. 7: Simple goals and projects
Ch. 9: Simple time management