Let me start with the negatives. The omnibus edition is so heavy I had to wear my wrist braces to hold it while reading. I can forgive this book being so long because it's an omnibus of three long novels; so no complaints here about the length of the story as I did with George R. R Martins first Game of Thrones novel. I'm not averse to long books, just books that go on too long.
Second nit-pick was the romantic sub-plot that runs through the three novels. I found it intruded into the plot and could have been edited without affecting either the main story or the protagonists development, but other people may well disagree.
The third nit-pick are the titles. For me, they were too on the nail and gave away the plot, but there again I'm a writer who has a background in psychological medicine, and I'm sensitized to things that seem obvious to me.
What I loved about this book was the biology, the way the aliens were described and developed and the overall story arc. It was a compelling read, as in I found time to pick the book up and dip into it, whenever I had a twenty minutes or so to read. This isn't a military SF novel despite the fact that the plot involves the destruction of worlds as an implacable alien force literally eats everything in its path. There are some descriptions of battles and skirmishes, but the focus is on the biology driving the aliens actions (there are several factions). And I really felt for the plight of the aliens who were not just humans with rubber foreheads.
So check it out, it's a hefty read, but well worth your time and effort.