It took me a while to get into the style, but it was worth the effort. I haven't read any Asimov for well over a decade and anyway this was written almost 50 years ago, and styles change, as have my reading tastes.
Please read this entirely subjective review accordingly.
So what is "The Gods Themselves"? A story based on the idea of exchanging energy between universes where the strong nuclear force is slightly different, written in three parts. Parts one and three are in our universe, and part two in the "para universe". The strong nuclear force is explained enough for the story to engage the reader who has no background in physics. In short, it is the force that governs how nuclear fusion works. A difference in values means there is a chance for energy exchange in *both* directions. At least that is the conceit, and as far as it goes it is backed by scientific fact (at least in models of the two universes involved).
The idea is explained well enough for non nuclear physicists to grasp, but this isn't Star Wars SF: no blasters, spacecraft or heated battles. Just a terrible existential threat to our solar system, and the inertia of a population wanting something for nothing and led by short-sighted and/or self-aggrandizing fame-hounds who have everything to lose either way, but don't care.
I rode along, gradually immersing more in the story, and being overcome with a sense of helpless fury at the inevitability of it all. The alien section started in what seemed to be a frivolous way that I feared would be a waste of reading time, but became perhaps the most emotionally engaging and angering part of the story.
I can't five star this, but I can't say why. It won both a Hugo and a Nebula when it was first published, about the best any SF novel can do, but it doesn't push my five-star button somehow. Without that oh-so cleverly done part two this would be a three star story for me despite the really clever idea at it's heart. Maybe it's because I'm too old and academic and political inertia are old tropes I've read about too many times. That might very well be it, in which case this book could well be a five star experience for you. I hope so.
I hope too that there is still an audience for this sort of Science Fiction, that not everyone sees SF as bound by the barely literate stuff coming out of the Kindle mill these days.