Want to know one habit ultra-successful people have in common?

They read. A lot.

In fact, when Warren Buffett was once asked about the key to success, he pointed to a stack of nearby books and said, "Read 500 pages like this every day. That's how knowledge works. It builds up, like compound interest. All of you can do it, but I guarantee not many of you will do it."

Buffett takes this habit to the extreme -- he read between 600 and 1000 pages per day when he was beginning his investing career, and still devotes about 80 percent of each day to reading.

And he's not alone. Here are just a few top business leaders and entrepreneurs who make reading a major part of their daily lifestyle:

Bill Gates reads about 50 books per year, which breaks down to 1 per week

Mark Cuban reads more than 3 hours every day

Elon Musk is an avid reader and when asked how he learned to build rockets, he said "I read books."

Mark Zuckerberg resolved to read a book every 2 weeks throughout 2015

Oprah Winfrey selects one of her favorite books every month for her Book Club members to read and discuss

And these aren't just isolated examples. A study of 1,200 wealthy people found that they all have reading as a pastime in common.

But successful people don't just read anything. They are highly selective about what they read, opting to be educated over being entertained. They believe that books are a gateway to learning and knowledge.

In fact, there is a notable difference between the reading habits of the wealthy and the not-so-wealthy. According to Tom Corley, author of Rich Habits: The Daily Success Habits of Wealthy Individuals, rich people (annual income of $160,000 or more and a liquid net worth of $3.2 million-plus) read for self-improvement, education, and success. Whereas poor people (annual income of $35,000 or less and a liquid net worth of $5,000 or less) read primarily to be entertained.

Successful people tend to choose educational books and publications over novels, tabloids, and magazines. And in particular they obsess over biographies and autobiographies of other successful people for guidance and inspiration.

There are many examples of successful people dropping out of school or foregoing a formal education, but it is clear that they never stop learning. And reading is a key part of their success.

If reading as a pathway to success isn't enough to get you motivated, consider these health benefits of reading: Reading has been shown to help prevent stress, depression, and dementia, while enhancing confidence, empathy, decision-making, and overall life satisfaction.

Whether reading is already a way of life for you, or you're just getting started, here are some book lists to consider:

9 of Warren Buffett's Favorite Books

17 of Bill Gates' Favorite Books

Books Extremely Successful People Read (From President Obama to Bill Clinton to Sheryl Sandberg)

20 books that the world's most successful people read and recommend

25 Must-Read Books for Success

And here are a few lists of 2016 must-reads:

10 Must-Read Business Books for 2016 (Inc.)

16 Must-Read Business Books for 2016 (Forbes)

9 Business Books to Read in 2016 (Stanford)

Happy (and successful) reading!

Andrew Merle writes about good habits for happiness, health, productivity, and success. Read more at andrewmerle.com and follow him on Twitter and Medium.

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