#4 Tesla Motors and SpaceX’s Elon Musk

Elon Musk says he's read thousands of books, but he really likes Douglas Adams' "The Hitchhiker's Guide to the Galaxy." He’s on a mission to space, so no wonder it is his favorite book. And he also likes Lord of the Rings series and he's read the work of many philosophers.

One of the biggest takeaways Musk got from reading Adams was, "The question is harder than the answer." "When we ask questions they come along with our biases. You should really ask, 'Is this the right question?' And that's hard to figure out," says Musk.

#3 Twitter and Square’s Jack Dorsey

Any new employees at his company ‘Square’ get a welcome kit and in it is a big red book, The Checklist Manifesto: How To Get Things Right by Atul Gawande. Gawande is a doctor and writer for the New Yorker. Its premise: A simple checklist can help people manage complex situations. Gawande uses a number of examples across a variety of industries, from medicine, technology and even disaster relief to illustrate his point. "Success metric for my work @Twitter: these books disappear from my desk. (you should read it too)," Dorsey tweeted in April.

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