In recent years a new and abundant attention has been paid to the Holy Spirit. This has precipitated a growing number of new devotees, especially those ranked as charismatics. Sometimes a newly found devotion focuses on selected and preferred Biblical passages, leaving the devotee possibly immune from a complete theology of Revelation, or solid theology of the Holy Spirit. Who is the Holy Spirit? serves a need in the midst of much recent charismatic literature. This is a well written and well reasoned work, based on Sacred Scripture, the Fathers and the Liturgy. The author stresses the traditional Catholic doctrine of the divinization of man through grace. At the same time the author is not abstract or excessively theoretical. In a practical way he applies the practical data on the Holy Spirit to a genuinely Christian daily living, involving a balance of inner awareness, prayer and exterior works. He also comments on the Catholic charismatic movement, seeing benefits in it, and also pointing up some of its potential dangers.