I would say that Abraham offering of Isaac was a in relationship of his 17 years of walking and growing in God. James is point out that one's work is evidences of one's salvation-just like Abraham's sacrifice of Issac was evidence of his 17 year walk with God.
But you don't need 17 years. The thief on the cross had only hours, yet our Lord said that he would be with Him in Paradise. So what was his work?
Joh 6:29 Jesus answered them, "This is the work of God, that you believe in him whom he has sent."
Good point. We Catholics refer to some things as mysteries because we were never meant or never equipped to know.
There are examples of those saved by faith alone and those saved by faith and works. The formula is a mystery, but ultimately we are all saved by the life and resurrection of Jesus.