You know reading adds to your store of knowledge. Maybe you've even heard it can improve your mental health, helping to boost self-esteem and creativity while fighting off depression and loneliness. But have you heard that sitting down with a good book can also increase your empathy?

Maybe that's why so many of the world's truly great business leaders are voracious readers. From Bill Gates to Warren Buffett, many icons of business are known to make time for good, old-fashioned reading. Among these book fans is Mark Zuckerberg. His New Year’s resolution this year was to get through a new book every couple of weeks, in fact.

As you'd expect from the founder of Facebook, he started a book club of sorts called A Year of Books on -- you guessed it! — Facebook to further this aim. Since January the group's nearly 500,000 followers have had the chance to read and discuss 16 books. What's the 17th?

An empathy workout.

This latest pick by Zuckerberg nicely illustrates the idea that reading can extend and strengthen your empathy. What is it? Portfolios of the Poor: How the World's Poor Live on $2 a Day by Daryl Collins, Jonathan Morduch, Stuart Rutherford, and Orlanda Ruthven. The much discussed 2010 book delves into the financial arrangements of the world's poorest citizens, the billions among us who make do with less than $2 a day.

It's an intriguing choice from a man who is worth somewhere north of $40 billion. Why did he select this particular book?

"It's mind-blowing that almost half the world -- almost 3 billion people -- live on $2.50 a day or less. More than one billion people live on $1 a day or less. This book explains how these families invest their money to best support themselves. I hope reading this provides some insight into ways we can all work to support them better as well," he explained on his personal Facebook page.

The book clearly represents a serious empathy workout, pushing Western readers to imagine the mundane details and stresses of life at the very bottom of the global economic order. Reading it might be worth considering if this is a subject you're not familiar with, not only for the inherent value in expanding your horizons, but also as greater empathy has been shown to improve leadership, further customer understanding, and help teams work together better.

What off-the-beaten-path book would you recommend to fellow entrepreneurs?