Having studied Genesis week in and week out, the main theme that has popped out at me has been that of uncompromising faith in the person of God. Calvin sums this up well:
It is the true test of faith and piety when the faithful are compelled to deny themselves in such a way that they even submit the affections of their human nature to God’s will, even though such affections are neither evil nor vicious in themselves – John Calvin, Commenting on Genesis 21:14
The passage is that of Abraham sending Ishmael and Hagar off into the desert, in response to God’s election of Isaac, “for through Isaac shall your offspring be named.” (v12). Now of course, this is but a preliminary sacrifice to that of Chapter 22, with Isaac on an altar. Nonetheless it seems like a major textual theme.