As an entrepreneur, it's hard to find the time to read. Summaries are great but a lot gets missed. Recently, I shared a popular list featuring the favorite books of 25 world leaders. From the response I grew curious to see where the greatest minds in business find inspiration and wisdom, especially since some of their daily challenges are much like my own.

Here is a list of recommended reading from 20 of the most successful and respected living entrepreneurs and executives. Many of their choices have no obvious connection to business and leadership literature, but have influenced their lives and careers in surprising ways. It's never too late (or too soon) to pick up a great book.

1. Sheryl Sandberg -Now, Discover Your Strengths By Marcus Buckingham & Donald O. Clifton. "This book has been instrumental in how we think about developing talent at Facebook."

2. Richard Branson - Long Walk to Freedom: The Autobiography of Nelson Mandela. In his book Screw It, Let's Do It, Branson cited Nelson Mandela's autobiography as a major inspiration.

3. Tony Hsieh - The Happiness Hypothesis By Jonathan Haidt; "This is probably the book that's made the biggest impact on my life over the past five years... The book is thought-provoking, and the concepts can be applied to business and life."

4. Dustin Moskovitz - The Lean Startup by Eric Ries; "At Asana, we've been lucky to benefit from Eric's advice firsthand; this book will enable him to help many more entrepreneurs answer the tough questions about their business."

5. Mark Zuckerberg - Virgil's Aeneid; Zuckerberg has recited lines from the famed work during product meetings.

6. Elon Musk - The Hitchhiker's Guide to the Galaxy by Douglas Adams; one of the major takeaways Musk got from book was that "The Question is harder than the answer." "When we asked questions, they come along with our biases. You should really ask, 'Is this the right question? And that's hard to figure out," Musk says.

7. Mark Cuban - The Fountainhead by Ayn Rand; "It encouraged me to think as an individual, take risks to reach my goals and responsibility for my successes and failures."

8. Jack Dorsey - The Checklist Manifesto by Atul Gawande; Dorsey gives this book to all of his new employees.

9. Jeff Bezos - Built to Last by Jim Collins; Bezos calls it "My favorite business book."

10. Bill Gates -My Years With General Motors by Alfred Sloan; "This is probably the best book to read if you want to read one book about business."

11. Steve Jobs - Atlas Shrugged by Ayn Rand; Steve Wozniak stated that the book was one of the "guides" of Jobs' life.

12. Tim Cook - Competing Against Time by George Stalk Jr. and Thomas M. Hout; Cook gives out copies to his colleagues and recommends it to new hires.

13. Warren Buffet - The Outsiders by William Thorndike; Buffet called it "an outstanding book about CEOs who excelled at capital allocation."

14. Marissa Mayer - The Charisma Myth by Olivia Fox Cabane

15. Indra Nooyi - The Road to Character by David Brooks; "Beyond provoking valuable self-reflection and introspection, it sparked a wonderful discussion with my two daughters about why building inner character is just as important as building a career. In fact, the two go hand in hand--the moral compass of our lives must also be the moral compass of our livelihoods."

16. Melanie Whelan - The Happiness Advantage by Shawn Achor

17. James Gorman - The Boys in the Boat by Daniel James Brown

18. Jeff Weiner - The Art of Happiness by Dalai Lama

19. Michael Bloomberg - How Will You Measure Your Life? by Clayton M. Christensen, James Allworth, and Karen Dillon

20. Oprah Winfrey - To Kill a Mockingbird by Harper Lee; "I remember reading this book and then going to class and not being able to shut up about it. I read it in eighth or ninth grade, and I was trying to push the book off on other kids. So it makes sense to me that now I have a book club, because I have been doing that since probably this book."