If you are building a product that is not yet released you should read this book. If you are building a product that is already released you should also read this book. If you are working on some overnight idea this is a must read! Why? In all cases it will help you to plan features, use data-driven approach for making decisions, and avoid waisting time by doing work that is not needed.
Eric Ries describes - on example of his own startup - how his team wasted weeks and months of development work, by working on features that turned out to be not needed nor wanted by customers. To avoid such pitfall, he is proposing different approach: create simplest possible prototype, release it and wait for users' feedback.
Lean startup is not only for startups. It is for everyone working on some product. From 1 person to international corporation. Eric gives great advice on how to evolve products and how to maximize your ROI (Return of Investment). He emphasize the importance of ability to reacting to feedback fast, not focusing too much on vanity metrics, but focusing on long term vision instead.
This book goes to my favorite books list!
If you haven't read it yet, I strongly encourage you to do so. If you did, share your thoughts in comments!