One thing that typically turns me a little sour on a book is lack of adequate research into a topic within it. In this case, it tuns out to be the effects of ballistic projectiles on objects. Dear Author, please don't use some lame movie or video series as the basis for the effects of a bullet on an object.
If that were my only beef, I'd have given this book more than two stars. Alas, the major thing that will turn me off about a book is ample evidence that it seriously needs an editor. Missing punctuation, poor word usage, typos, and the inability to know when and where to put a break between one paragraph and the next were constant annoyances to the editor in me. Disconnects like saying one of the main characters had never "lost a man on his team" and then later having an extensive scene where he laments just such a loss is just one example; however, the most egregious case was an instance where one statement was followed on the same page by a contradictory statement. Specifically, and relevant to my first peeve, it describes a box that had been struck by a bullet as having one corner collapsed and a gaping hole in the other side—an indication that the bullet passed through the box. A few lines later, it describes how a couple of photo albums stopped the bullet, so now it didn't pass through the box. That and the fact that a bullet passing through paper doesn't tear it into tiny shreds as is described here should be evident by the fact that in competitive shooting sports, a bullet passes through a paper or cardboard target leaving nothing other than a neat, round hole. I won't even go into how a makeshift bullet-resistant vest can be made from layers of magazines.
It also seemed that the author was doing something I find truly, truly annoying, and that's padding the word count. The result? The story dragged in areas.
With a little work, this book could shine. As is, it needs some careful review of the content with a serious eye to at least not leaving a sentence without a period at the end.