Though Bill Gates has been out of the Microsoft game for nearly two decades, he still hires top talent. The Bill & Melinda Gates Foundation has almost 1,500 employees and an ambitious mission to help all people lead healthy, productive lives.

When Gates recently spoke at his high school alma mater, he was asked what competencies he looked for when hiring for leadership roles. 

"The skills are a myriad," Gates said. "We need people who have spent their lives working in the field to know what it's like."

He says the foundation hires about half of its employees from the private sector because they have cultivated skills like measurement and looking at demand. They also hire people who have spent their careers working with government, which is key to the foundation being able to do its work well. 

One quality Bill Gates looks for beyond the résumé. 

Despite the wide range of expertise and skills needed at the Bill & Melinda Gates Foundation, many hires share a common trait. 

These leaders aren't just passionate about improving health and education. They are fascinated by the past, present, and future. They have a deep curiosity about the state of these problems worldwide that leads them to become voracious students of what's working and what's not. And they read--a lot. 

To be a great leader, you must be a lifelong learner

"The only common in these people is a fascination of the progress that is taking place and the progress that hasn't taken place," Gates said. "They're really a student of those things."

Two fundamental books new hires should read.

It will come as no surprise that Gates--an avid reader himself--expects new leaders who join the foundation to be well-read. "Have they been reading about the topics of interest in a pretty deep way?" he said. 

Gates cited two books in particular that are fundamental for employees at the foundation to read. 

Factfulness: Ten Reasons We're Wrong About the World--and Why Things Are Better Than You Think

In Factfulness, Hans Rosling challenges our perception of the developed and developing world. Instead of relying on unconscious and predictable biases, he encourages readers to adopt a different framework for understanding poverty, education, and health worldwide. 

"This is one of the most educational books I've ever read," Gates has previously said. "It covers a space that it's not easy to go learn about. The world would be better if literally millions of people read the book."

To get a sense of what the book covers, check out the TED Talk from authors Hans and Ola Rosling, "How not to be ignorant about the world."

The Better Angels of Our Nature: Why Violence Has Declined

Cognitive scientist Steven Pinker spans the history and psychology of violence over 700 pages. Gates wrote on his blog in 2012 that it stood out as one of the most important books he's ever read. 

"The book is about violence, but paints a remarkable picture that shows the world has evolved over time to be a far less violent place than before," Gates says in his review. "It offers a really fresh perspective on how to achieve positive outcomes in the world."