I'm not a professional critic, but I am a bit picky when it comes to realism in show. Invasion is slow to unfold, my only complaint, and leaves me hanging for more content by the end of the episode. But it's not a physics violating, causality doubting, unbelievable hero movie, and thus far has my attention. It's not a typical alien invasion movie where the expectations are set in the first 10 minutes. This is about the Human perspective. So far, I have found it entertaining. If it takes a hard turn into an 'Independence Day' level motion picture disaster, I will promptly revise this review accordingly.
Earth is big. If a real hostile alien invasion occurred, it would not be known everywhere right away. There would not be spaceships hovering over your city. Even if you'd heard about an invasion in the news, you'd still probably do the same things you've been conditioned to do until that reality impacted you. When it did, there'd be confusion, chaos, and hostile interactions with other humans; because other humans are usually our biggest enemy. Communications would be the first technology compromised, simply because our network is designed for ratings and money, not emergencies. If an entire city disappeared on the other side of the planet, and it wasn't on Twitter, you might not know about right away.
This show unfolds in exactly this way, while focusing on a few unrelated character perspectives from around the world. The only information you have, outside of already knowing what the show is about, is pretty much what the characters know. It might have been better if they hadn't called it 'Invasion' to eliminate any bias going in and let the viewer be captivated by the unknown. It's better to come to the conclusion that this is an invasion when the characters begin to realize it.
Recap/revision: OK, things did get a little weird, and it drags anti-climactically all the way out. I will, however, retain my rating of 4 stars, solely on some of the more interesting moments and scenes (no spoilers). There were hints that this could continue in a more-engaging way with a second season; perhaps with a larger and more formidable military response, or maybe a perspective shift. The show wasn't amazing, but it was good enough to keep me interested for 10 episodes, so I'll probably sit for another season if they decide to continue the story. In fact, there may have been enough crumbs dropped in season one to make an amazing cookie later.