If you want to change the world, there's no better place to start than with the clothes on your back and the shoes on your feet. I'm not being dramatic. I believe it to my core. A look at the facts: Apparel is a 2.5-trillion-dollar business that holds up 3 percent of the global economy and employs hundreds of millions of people around the world, mostly young women.

Clothes are our most personal and universal possession. I bet you're wearing the stuff right now.

And yet the clothing industry is a far cry from the empowering, innovative, and uplifting force it should be. It is instead among the world's largest carbon emitters, water polluters, and users of toxic chemicals. As much as 8 percent of carbon emissions are caused by fashion. A third of the microplastic pollution junking up our oceans is coming from what we wear. A garbage truck's worth of unwanted fashion is landfilled in the United States every two minutes. And in an industry that makes some people so fantastically rich and famous, there are somehow only a handful of garment workers earning a living wage anywhere.

More people than ever are aware of clothing's negative social and environmental impacts and want no part of them. No one wants to feel guilty when they get dressed in the morning. We want and expect to feel good in our clothes.

As I've learned, building a more conscious closet takes effort. Anything worth doing does. But it isn't hard or unstylish or expensive. It can be easy and beautiful and accessible to anyone, including you. Beyond that, it will help you get off the fast-fashion treadmill, regain your shopping sanity, and uncover your personal style. All while saving you money. It can change the world. And it will change your life.

I know because all of this happened to me.

Eight years ago, I set out to write my first book, Overdressed: The Shockingly High Cost of Cheap Fashion. As I boarded a plane to investigate the sweatshops in Bangladesh and China, my closet was overflowing with clothes that I didn't like or care about. I recycled, shopped for organic food, used reusable shopping bags, and yet I was ignoring the enormous environmental crisis lurking in my closet. I rarely felt confident or happy in what I wore, despite owning 354 items of clothes. I was trapped in a sad clothing cycle, and I was eager to find a way out of it.

Overdressed was one of the first investigations to draw a straight line between our increasing consumption of fashion and the critical problems of climate change, pollution, and poor working conditions. Driving it all was the meteoric rise of "fast fashion," a hyperaccelerated cycle of making, consuming, and trashing clothes that is wrecking our environment and keeping workers locked in poverty. After the book came out, countless people turned to me wanting to know how to dress with their values. They asked, "How should I shop? What's okay to wear?" The truth is, I was often asking myself the same questions.

I struggled at first to build a conscious closet. I bought rainbow-colored eco-shoes and sewed a homemade lavender mesh top so amateurish it would have gotten me kicked out of home economics class. I stood up at a gathering of other conscious-fashion experts one winter's night after my first book's release and pleaded, "Please, someone just tell me what to wear!"

In recent years, struggle has become progress. Before my eyes, sustainable and ethical fashion has transformed from a niche cause to a worldwide movement (you'll hear plenty from and about those movement leaders in this book). New reports and...