Getting 'the gospel' right is key. It's a matter of much angst for us evangelicals. Galatians is so often my go-to book, and here's a little of why, from Charles Cousar
"The fundamental nature of the gospel is grace... the preaching of Christ's gospel will inevitably convey God's grace not in an abstract of theoretical fashion, but in terms of the particular human situation. It may include judgement as well as mercy, imperative as well as indicative, and appropriately so, if arising from or leading to the word that God is for us. If there is a test to be applied to preaching, it is this: Does it declare Jesus Christ as the unqualified liberator - from religious legalism or secular cynicism, from paralyzing apathy or frantic anxiety, from being oppressed or being the oppressor, from coward fear or brash self-reliance? And as Paul will go on to say in Galatians, does this preaching clarify what Christ as freed us for? Secondly, the gospel is more than a set of propositions about Christ, his death and resurrection (though obviously it can and must be so stated); it is a divine activity my mean of which people are drawn into the realm of God's grace. Paul makes a surprising equation. The Galatians who depart from the message they had previously accepted and followed the theology of the agitators are deserting not merely a doctrine but God himself, "him who called you". To abandon the gospel is to forsake God"
Charles Cousar on Galatians in the Interpretation Commentary