Mysticism is Evelyn Underhill's seminal work on the subject.

The book is divided into two parts, "The Mystic Fact" and "The Mystic Way."

In the first part Underhill explores the theological, psychological, and philosophical underpinnings of mysticism from a historical perspective.

In the second part Underhill examines the application of mysticism in one's life as a means for spiritual growth.

Evelyn Underhill's Mysticism is both a fantastic introduction to the search for spirituality through mysticism and an almost encyclopaedic examination of the subject.