With regard to reading Barth, a required standard in my Romanist seminary days, my standard answer is:
1. Read The Doctrine of God: The Election of God; The Command of God first (Volume II, Part 2)
2. Next read all of Volume IV Chronologically
Volume IV Part 1: The Doctrine of Reconciliation
Volume IV Part 2: Doctrine of Reconciliation: Jesus Christ the Servant As Lord
Volume IV Part 3, 1st and 2nd halves: Doctrine of Reconciliation: Jesus Christ the True Witness
Volume IV Part 4: Doctrine of Reconciliation: The Foundation of the Christian Life (Baptism) (was never finished and can be skipped as it is not one of his finest efforts)
By the time you finish with the above, you will be smart enough about the man to decide where you want to go next. My favorite would be to read Volume II Part 1: The Doctrine of God: The Knowledge of God; The Reality of God.
But, having said all of that, I recommend you find Webster's Barth (see
here) for a starter read to get the lay of the land.
A few of my favorite Barthisms:
“In the Church of Jesus Christ there can and should be no non-theologians”
“Jesus does not give recipes that show the way to God as other teachers of religion do. He is himself the way.”
“Faith is never identical with piety.”
“Grace must find expression in life, otherwise it is not grace.”
“Man can certainly keep on lying... but he cannot make truth falsehood. He can certainly rebel... but he can accomplish nothing which abolishes the choice of God.”
“All sin has its being and origin in the fact that man wants to be his own judge. And in wanting to be that, and thinking and acting accordingly, he and his whole world is in conflict with God. It is an unreconciled world, and therefore a suffering world, a world given up to destruction.”
“He {God} is not deaf, he listens; more than that, he acts. He does not act in the same way whether we pray or not. Prayer exerts an influence upon God's action, even upon his existence. That is what the word 'answer' means. ... The fact that God yields to man's petitions, changing his intentions in response to man's prayer, is not a sign of weakness. He himself, in the glory of his majesty and power, has so willed it.”
Barth is an acquired taste for the mature Christian interested in philosophical theology (my specialty) who is able to separate the wheat from the chaff.