The Social God and the Relational Self: A Trinitarian Theology of the Imago Dei (2001) by Stanley Grenz on the recommendation of Larry Crabb. When I attended his School of Spiritual Direction, there were several books and authors that he mentioned. Other than CS Lewis, who he mentions frequently, Crabb often spoke fondly about this book.
The Social God is an ambitious academic text. In seeking to explore the relationship between the Trinity, our notions of self, and the Imago Dei, Grenz covered a lot of ground. Briefly, he discusses numerous theologians from Iranaeus to Calvin to Barth to Moltmann. He also dives deeply into the psychological literature of the self from William James to Sigmund Freud to Abraham Maslow. Throw in discussions of Nietzsche, Kant, and Locke and you have a broad exploration of God in relation to the self.
I will confess that this was a challenging read for me. Academic neuropsychology is often difficult enough, not to mention a broad-ranging academic theology that relies, in some cases, on reference to original Greek, Hebrew, and Aramaic. He also seemed to be balanced in his approach. Regardless, I found my thinking challenged, trying to understand topics like Rahner's Rule, the LaCugna Corollary, and the economic versus immanent Trinity. At at a more base, or practical level, this book was helpful to me in terms of understanding the importance of relating as a component of the Imago Dei. The penultimate chapter on The Imago Dei and Human Sexuality deserves a second read as it explores how the Imago Dei may be specifically expressed in our maleness and femaleness. I suspect that in what he wrote, both conservatives and liberals could find something with which to be offended.
I would recommend this book, but it is not for the faint of heart.