Igneous Quill

If you are looking for a simple, introductory study of the Trinity, this probably isn't the book for you.  Despite its relative brevity (240 pages), The Tripersonal God is a depthy book with plenty of Bible references and notes to chase down.  

The writer, Gerald O'Colllins, S.J., takes the reader through the history and development of the doctrine of the triune nation of God, beginning with the Hebrew Scriptures and working his way into modern times. Thus the approach is structured along historical lines, rather than broken up into categories usually employed by systematic theology.  This strategy works well, for the most part.

There are a few things in particular that I really appreciate about this book, aside from its structure.

First, the writer (a Roman Catholic theologian) does not hesitate to quote cite those books identified outside the Roman Catholic and Orthodox communions as "apocrypha." From a Protestant perspective I appreciate the inclusion of Old Testament apocryphal sources, as it contributes to understanding the popular mindset and understandings that were current in the times of Jesus, his disciple and the early church.

Second, Rev. O'Collins accepts and utilizes the perspective of contemporary higher criticism.  Although I have my doubts about some aspects of higher criticism, O'Collins manages to handle this method of scripture analysis intelligently and faithfully, never undermining the core essentials of the Christian faith nor denying the role of the canon in shaping our understanding of God's nature.

Third, with plenty of notes and citations, one can easily spend a rewarding few weeks or even months exploring the information presented.

Though I would by no means recommend this book to someone just starting out on their exploration of the topic, it is a very good text for anyone who is willing to take some time and do some serious thinking about the Trinity.