Here's a summary of my thoughts. Because of this volume's lack of complexity, there's really no need to dive in and dissect every aspect.
Knife is a collection of stories that have characters with American names and inner turmoil. This "inner turmoil" is never resolved by any story's end. In fact, there is only just enough time to inform the reader what the character's/characters'problems are before it moves on with a little ...whatever it is they do until the pages run out.
These stories were written in the 90s so it has the archaic look about them, and though I really dislike the old-fashioned manga style of the 80s and 90s, it worked in this case. It was actually well done and I didn't mind looking at it.
Every character in every story was pretty much one-faceted with no growth whatsoever. They served to be the catalyst or the "rock" for the other suffering character or simply a "prop" that the story revolved around. They served their purpose for their own problems (which were more-often-than-not never solved in the first place) and truthfully they returned right back where they started mentally or emotionally.
I do think that the mangaka placed their feelings and mental state quite adequately within the allotted time without drawing it out or hamming it up. For me, the limited reasoning behind each character was upfront within the first two or three pages and was out of the way so it wasn't one of those "big, dramatic reveals" of why they acted how they did at the end and the reader just has to sit there and go "well..what the hell, then!".
Overall, this is a quick read for someone who's looking for an adequate collection of stories that doesn't require any emotional investment or even much attention devoted to it, as if skim it you'll still be able to comprehend what's going on. Read it just to read it, don't do it because you think you'll find a gem.