What is Marianne Williamson's definition of God? What's her personal prayer? Watch as she answers these questions and more in a round of Soul to Soul.

Twenty years ago, Marianne Williamson's groundbreaking book, A Return to Love, became a global phenomenon that helped open the heart space of millions Published in 23 languages, it spent 39 weeks on The New York Times bestseller list. The book so moved Oprah that she bought 1,000 copies, gave them to her audience and invited Marianne on The Oprah Winfrey Show.

Now, 20 years later, Marianne returns to Chicago to discuss her landmark work. Watch the clips below to find out just how powerfully the life lessons from A Return to Love still resonate today.

Oprah shares her favorite passage from A Return to Love:

Why Marianne says we're both better—and worse—off than we were 20 years ago:

How to recognize the miracles that already exist in your life:

Why Marianne says we should all pray for those who've wronged us:

This Sunday, Oprah and Marianne Williamson are sitting down to talk about what's happened in the 20 years since Marianne's book, A Return to Love, changed the lives of millions.

Today, we've got an excerpt of Marianne's new book, The Law of Divine Compensation.

We carry a lot of misconceptions about love. Putting love first isn’t a life of “sacrifice,” for example, as many have been taught. In fact, putting love first means knowing who you are, which means accepting the fact that you’re entitled to miracles. Putting love first means knowing the universe supports you in creating the good, the holy, and the beautiful. It means knowing you’re on the earth for a purpose, and that the purpose itself will create opportunities for its accomplishment.

Making love your bottom line doesn’t make you “lose.” Putting love first is ultimately the way you inevitably gain. For what you give, you shall receive; and what you withhold will be withheld from you. Most of the world’s religions share this core idea. Or, as a friend of mine once described the idea to me, the universe keeps a perfect set of books. You give love; you get love.

Making love the bottom line doesn’t mean you have to give everything away or that you’ll never charge for your services. The principle of fair exchange gives love to both giver and receiver.

Making love the bottom line doesn’t mean you’re compelled to do anything anyone ever asks you to do. Love always gives the loving response, but sometimes the loving response is “No.”

Read more of The Law of Divine Compensation

Author Marianne Williamson says her life was forever changed 20 years ago by a phone call from Oprah. Read her reflections on that time and the full circle moment she had taping this week's "Super Soul Sunday."

Then, tune in Sunday at 11 a.m. ET/PT to OWN.

By Marianne Williamson

My appearance on this week's "Super Soul Sunday" is to celebrate the 20-year anniversary of the publication of my book A Return to Love.

I remember sitting in my apartment in West Hollywood 20 years ago when I got a call from Oprah Winfrey. She was a huge star already, of course, but her book club had not yet begun, and in some ways, our whole society was a bit more innocent. I was excited she called, and I enjoyed talking to her. But I had no idea she was about to change my life. A week later, she'd be telling her huge TV audience how much she loved my book—and that she'd bought a thousand copies to give away. A Return to Love then became the fifth-highest-selling book in America that year.