Written by a professing Christian, who is nevertheless sympathetic to mysticism, this volume does an excellent job of covering the material in a readable form. Admitting that mysticism is a slippery term with many definitions, Harkness decides that mysticism has more to do with communion with God than union. Her understanding is that mysticism is a direct and immediate awareness of the presence of God, whether in union or communion. This awareness brings fresh insight, which the mystic believes come to him from beyond either sensory experience or logical deduction, as well as a joyous sense of the Divine Presence (p. 35).
Mysticism is excellent on the history of mysticism, giving solid overviews of important mystics from the past. There is also good coverage of modern mysticism and semi-mystics from Zen to tongues. Where Harkness falters is in her attempts to explain biblical mysticism. She fails here because she is unable to distinguish between Divine revelation and the experiences of true mystics who are attempting a union with God that is unexplainable through the intellect. There is a vast difference between the Divine encounters in Scripture and the divine encounters of the mystics. Our author fails to understand this difference.