Here's what I'm looking for in a beta reader: constructive criticism. By that, I mean tell me anything that you like or dislike about the book (perhaps with a suggestion for how to fix problems). Comments like "I liked it" or "It sucks" aren't really all that helpful. Comments like, "In Ch. 3 where you said Daniels did [fill in the blank], I found the description confusing." or "I thought the scene in Ch.9 where the aliens did [fill in] didn't have as much tension as it should have" are much more helpful.
Feel free to comment on anything you want: pace, dialog, action sequences, the flow of the story, etc. I'm not expecting pointers to typos, punctuation, grammar, etc., (although you're welcome to point those out, too, if you feel like it). I'm mainly concerned about the big stuff. Is it interesting? Did you like the characters? Do I need more backstory for some of them? Should I include more information about the alien homeworld, or other details about them? Is the technology and military stuff convincing and interesting, and so on.
I don't want to make the process onerous for anyone. But the more info you give me, the better the book will turn out. Hey, If you're really helpful I'll even acknowledge you in the "front matter" of the book. How 'bout that?
To all beta readers, I hope you enjoy the story!