The main place of Isaac in the Bible is as a demonstration that when one utterly depends on God, God will provide the way, and thus, no task or trial is beyond the strength of the one who makes God their strength.
Abraham waited quite a while to start trying to have kids, and by the time he got there, his wife, Sarah, was a bit old for the task. However, God had promised that the descendents of Abraham would be as numerous as the stars, or sand at a beach, or whatever "hah, it's really fairly uncountable, though you probably could give it a shot if you had a computer, which nobody will invent for 5000 years, so why are we still talking about this?"
Sarah even, at one point, sneaks in her handmaiden Hagar, figuring that they may as well start the whole descendent thing going, even if not by the direct literal wifish means. This is seen by God and by Abraham as being rather sneaky and not what God had in mind, and Hagar is sent away with her son Ishmael to start the whole Palestine/Philistine thing going hard core, because God is a firm believer in one's mistakes having consequences, and because life is tough like that.
Finally, at somewhere near a century old (give or take 5 years as per anuam percentage, compounded anually) Sarah conceives Isaac, and Abraham goes off on a Dennis Leary style rant about how powerful his sperm is, thank the Lord.
And then, a number of years afterward, the Lord says "Okay, Abraham, I need you to come up on this mountain a couple of days away...yes, you can charge your walker first...and make a sacrifice to me. Oh, and it's the boy."
It's a test of character, and of faith, and a whole bunch of other stuff. And yes, God has done the impossible and had Sarah have a kid at WAY past menopause, so hey, he should be good for it, whatever that entails. But of course the human reaction is "Er...how gauche."
But Abraham goes and does it. He takes Isaac up a hill, carefully telling him that it's a science trip, and he's going to show him that thing with the magnifying glass and the ant, and he's just laying him on this altar because, honestly, he hasn't seen all of the things he can do as a chiropractor...
And just as he's about to run the kid through, the dagger's dropping, etc., the Angel of the Lord steps out, grabs Abraham's hand, and says "landshark?" and presents him with a goat.
It becomes very easy to be flippant toward the story after years of hearing it in sunday school over and over, and becoming rather sick of the 2 dimensional manner in which it's presented, and because, quite honestly, just because we're sick of a cliche doesn't mean it isn't true...
But it is true. I can't count how many times I've been up the creek, it's on fire, etc. and God pulls it out of the hat that I wasn't even aware I was wearing. This does happen. Beyond all belief, beyond all reason, things happen. And then the next time I'm asked to step out... I balk again, and the cycle continues.
P.S., There are also voices, now and again, about how Ishmael was actually the first born from Abraham, and so Israel's not the proper nation, but the Palestinians, or something. But the bible is very clear on how proper first borns are to be, within wedlock, etc. You can shake your fist all you want and scream "but our book says..." which is fine. But if that's so, then why are you bothering to argue about a story in another book?