Caprica is great science fiction in the soft sense of the word. That is, there are no big starship battles with phasors and no one gets sucked into a quantum singularity and no one shapeshifts or teleports anywhere. Frankly, you can't even tell it wasn't set in 2012, or even 1972.
And it really has essentially nothing to do with Battlestar Galactica. Which just makes it all that much better.
But it does have the subtle tone of the near-future, told via its personal impacts on individual lives. Its characters live in a world you can identify with, full of concerns about money and status and health and beauty and sex, and not some 23rd century version of Star Trek, where no one seems the least bit concerned about money or fatty foods or loneliness or their own damn neuroses that can ruin everything.
People in Caprica are real. They love. They hurt. They do stupid things for stupid reasons. And they can't escape their times, meaning the future rolls over them just as much as they do the rolling.
You'll learn how the Cylons were born -- but that could have occurred a hundred different ways. The real reason behind their creation comes down to one reason, as it always does -- human weakness. We want what we cannot have. And it inevitably leads to our downfall.
Rent it. Download it. It doesn't matter is you've ever seen BG. Start anew.