I have a strong distaste for books that end with a cliff hanger, expecting you to buy more books in the series to resolve the plot. Series books are great and there are many I like, but I strongly prefer a series so compellingly written that you want to read more of them, over a story that ends with a cliff hanger in an attempt to prod you to read more.
That said, the book is OK, but pretty darn derivative. The “aliens conquer earth” genre is pretty well-worn and an author really has to stretch to do something original with it. Alas, that didn’t happen here. The characters are OK, but often behave in ways I certainly wouldn’t. The world-building is a little naive and unscientific for my tastes.
There is action and wonder, but in service of goals I personally dislike. Your mileage may vary.