Recently I was interviewed for the very excellent Pilgrim's Podcast, which episode you can find here. I said in the podcast that I'd post some resources, and these are they
For those wanting to get a good grasp on the thought of the early church about the Trinity, Tarmo Toom's Classical Trinitarian Theology: A Textbook is great for beginners and the advanced alike. He begins very simply, and is careful to explain technical terms and details in a clear manner, and takes you through the controversies and periods of the early church to see how the traditional understanding of the Trinity emerged.
For those coming from an evangelical background, there are two fine introductions to the Church Fathers. One is by Bryan Litfin, Getting to Know the Church Fathers: An Evangelical Introduction, and is readily accessible. The other is a number of books by Christopher Hall, Reading Scripture With the Church Fathers, Learning Theology With the Church Fathers, a third more recent book Worshiping With the Church Fathers, and a fourth is envisaged. I would try and pick up one of the first two books by Hall if that was something you wanted to pursue. Both authors write with a view to evangelicals and a popular audience.
On impassibility, the situation is more difficult. The most thorough-going defence of impassiblity in a modern context is by Fr. Weinandy, Does God Suffer? It's not a light book, but it is excellent.
A good companion to this is the book by Gavrilyuk, The Suffering of the Impassible God, which investigates specifically the doctrine of impassibility in the Fathers. Gavrilyuk is significant for his refutation of the common conception that impassibility is an unbiblical idea that is imported by Greek philosophy.
More accessibly, Kevin DeYoung did a recent presentation at Together for the Gospel conference: his notes are available from this blog post, while the audio is can be found on this page.
Hope this is of help to some.