Reddit reviews Historical Theology: An Introduction to the History of Christian Thought

Alister McGrath's "Christian Theology: An Introduction" was super helpful for me.
He also has another called "Historical Theology" which I have yet to read, but have heard many great things about. He does a great job of tracing Christian theology throughout history, and framing it in a digestible, easy to understand way.

For a good textbook overview, McGrath has a great book called Historical Theology

He also has a book exclusively about justification, since you mentioned that above. I read these as a teenager, and they proved to be great starting points.

Otherwise, check out the sidebar to r/christianity for online reading of classic authors. Read some basic treatises like Augustine's Nature and Grace, Luther's on the Freedom of a Christian, and Introduction to Romans.

I'll always plug my man Gerhard Forde, too :) Books like Where God Meets Man and On Being a Theologian of the Cross are short, accessible books with a perspective that I think is very helpful in approaching the "problems" of God and faith. Justification is his main theme.

Also, just curious, what's your username about?