"Strive for excellence in few things, rather than good performance in many."
The book gives great insight into how you can become more effective both in your personal life and in your work or business. It puts you in the mindset that not all inputs produce an equal amount of outputs by showing the Pareto principle in action.
1) In business, optimizing the range of your services and products can have the biggest impact on your success.
2) Accept the imbalances and unfair-ness in day-to-day life as well as in business, so that you can use all that to your advantage.
3) The 80/20 principle (80% of results come from 20% of all efforts) is one of the key strategies of highly effective people and organizations.
READ IF: You tend to do a lot of things at once, if you have competing priorities or way too many stakeholders / clients to please.