"Proof of God", by Swami Vivekananda

"His vast knowledge of Eastern and Western culture as well as his deep spiritual insight, fervid eloquence, brilliant conversation, broad human sympathy, colourful personality, and handsome figure made an irresistible appeal to the many types of Americans who came in contact with him." - Ramakrishna.Org

Here is an interesting article about the Swami which appeared on the cover of the New York Times Sunday Book Review a few years ago: "How Yoga Won the West"