The Triune God
If you are planning to teach or to write on the Trinity, then this is a must read. If you are looking to multiple books to study on the Trinity, make this one of them. The author emphasizes the process of the development of the doctrine of the Trinity from revelation, for which I am very thankful. Historical development and tradition are not absent, but are not the primary focus. This is certainly not a book for the beginner, but for those who have a introductory knowledge of the doctrine already: pick this up and read. Much wisdom will be gained by it.