India, Sept. 28 -- What happens when the descendants of two of the 20th century's most impactful thinkers meet in New Delhi through a common friend? They fulfill their destiny set in motion nearly 200 years ago, and write a book together.

On September 30, Truth and Love: The Gandhi-Tolstoy Letters, written by Daniil Tolstoy and Gopalkrishna Gandhi, and published by Penguin Viking, will hit the stands, bringing to light a little-known but deeply transformative exchange between Anna Karenina author Leo Nikolayevich Tolstoy and Mohandas Karamchand Gandhi.

Tolstoy, an academician and publisher based in Sweden and the Russian author's great grandson and Gandhi, a retired diplomat, author and the grandson of Mahatma Gandhi, met in the capital...