This book provides an entrée into the Tantric (or Vajrayana) Buddhism of Tibet, as conveyed by Tibetan masters teaching in the West, and as received by their Western students. The Tantric tradition is a unique collection of lesser-known texts, concepts, and meditation practices that are usually made available only to experienced and specially initiated practitioners. The "Vajra World" (vajradhatu in Sanskrit) is a realm of indestructibility, the level of reality beyond all thought and imagination, all impermanence and change, which a fully realized person knows and inhabits. Used metaphorically, "Vajra World" refers to the traditional culture of Tibet and the unique spirituality that is its secret strength. Topics include: The tantric view of human nature and the external world The special role of the guru, or tantric mentor The preliminary practices that prepare the student for full initiation The major dimensions of Vajrayana practice, including visualizations, liturgies, and inner yogas The tradition of the tulku, or incarnate lama The lore surrounding the death of ordinary people and of saints The practice of solitary retreat, the epitome of traditional Tibetan Buddhism Secret of the Vajra World is the companion volume to the author's earlier book, Indestructible Truth: The Living Spirituality of Tibetan Buddhism. While that book focuses on the history, cosmology, philosophy, and practice of the more public, exoteric side of Tibetan Buddhism, this work treats its more hidden and esoteric aspects as they take shape in Vajrayana. Together, the two volumes provide a broad introduction to the major traditions of Tibetan Buddhism.