Jason Byasee, Trinity: The God we don’t know (Abingdon Press, 2015) — short, accessible introduction.
David Bentley Hart, The Experience of God: Being, consciousness, bliss (Yale UP, 2014)
Walter Kasper, The God of Jesus Christ (Bloomsbury Continuum, 2012)
G. L. Prestige, God in Patristic Thought (SPCK, 1952) — older but valuable study
Katherine Sonderegger, Systematic Theology, Vol. 1 God (Fortress, 2015)
Denys Turner, The Darkness of God: Negativity in Christian mysticism (CUP, 1998) — on the mystery of God
Thomas Weinandy, Does God Suffer? (U of Notre Dame Press, 2000) — excellent discussion of this controversial question.
Short, gentle introductions
David Ford, Theology: A very short introduction, 2nd ed. (OUP, 2014)
Kelly M. Kapic, A Little Book for New Theologians: Why and how to study theology (IVP, 2012)
Michael Lloyd, Café Theology: Exploring love, the universe and everything (Alpha, 2009)
Ronald F. Thiemann and William C. Placher (eds.), Why Are We Here? Everyday questions and the Christian life (Trinity, 1998)
Sam Wells, What Anglicans Believe: An introduction (SCM/Canterbury Press, 2011)
Rowan Williams, Tokens of Trust: An introduction to Christian belief (Canterbury Press, 2007)
Rowan Williams, Ponder These Things: Praying with icons of the Virgin and The Dwelling of the Light: Praying with icons of Christ (Canterbury Press, 2002 and 2003)
Several distinguished theologians have written commentaries on the Apostles’ Creed. There are two, both titled Credo, one by Karl Barth (translation from Hodder & Stoughton, 1964) and one by Hans Urs von Balthasar (translation from Ignatius Press, 2000).
John Pearson’s Exposition of the Creed (first published in 1659) was for centuries the mainstay of clerical education in England. A notable curiosity is John Mason Neale’s children’s book, Tales Illustrative of the Apostles’ Creed (Masters, 1857).