For years, women have been continually gaining ground in terms of getting an education. In the early 1980s, women became 50 percent of the college graduates in the United States. Yet women still aren’t making it to the top leadership positions. As of June 2016, only 21 Fortune 500 CEOs — 4.2 percent — are women. As of January 2012, women only led 17 of the 195 independent countries in the world.

This disparity is precisely what Sheryl Sandberg addresses in her 2013 book Lean In. Sandberg, the current COO of Facebook and an early Google employee, was inspired to write the book after the overwhelming response to her December 2010 TED Talk, “Why we have too few women leaders.” The book’s publication prompted Sandberg to found LeanIn.Org, a nonprofit organization that supports women through an online community, educational lectures and Lean In Circles, small groups that meet together monthly to encourage each other.

“Lean In” is infused with research about working women, corporate America’s habits and family dynamics. One of the most prominent studies Sandberg cites is the Heidi/Howard case study. Students at Harvard Business School were split into two groups. One group was given information about a real-life entrepreneur named Heidi Roizen who had an “outgoing personality” and an expansive professional network. The other group was given the same information with only one minor change — “Heidi” became “Howard.”

The results? The students saw Heidi and Howard as equally competent, but Howard seemed like a more appealing coworker. Heidi, on the other hand, seemed selfish and not “the type of person you would want to hire or work for.” Even though Heidi and Howard had the same accomplishments, Howard was more likable simply due to his gender. This dynamic, Sandberg notes, plays out again and again in the workplace. Successful working women are often seen as “too aggressive” or “bossy.”

But “Lean In” isn’t only full of research. Sandberg uses a conversational, easy-to-read tone and regularly infuses stories from her personal life. She explains how even she sometimes fails to notice and correct the gender gap. After giving a speech to a group of employees at Facebook, she took questions from the audience for a short period of time. Later that afternoon, a young female employee came to her desk and explained that at the end of Sandberg’s talk, she said she’d only take two more questions. After she answered two questions, all the women in the room put their hands down. But a number of men kept their hands up. Sandberg continued to answer questions — but only from the men. “Even though I was giving a speech on gender issues, I had been blind to one myself,” Sandberg writes.

What can we do to confront such gender issues? Work toward equality. “A truly equal world would be one where women ran half our countries and companies and men ran half our homes,” Sandberg writes. “I believe that this would be a better world.”

“Lean In” highlights everything from the myth of “having it all” to finding a fully supportive partner or spouse. Sandberg touches on mentorship, why careers are like jungle gyms rather than ladders and the difficult decision many women must make of whether to keep working after having children. The book isn’t just an inspiring read for women — it’s also a powerful book for men who want to work toward equality. Pick up a copy of “Lean In” and learn why women need to “sit at the table,” “keep their hands up” and “lean in to their careers.”