We've long heard the oft-cynical refrain that there is nothing new under the sun, but, in the case of Kuroneko, at least, that's actually true.
If you've seen Oreimo—and, let's face it, it's unlikely that you haven't, if you're interested in this book—there isn't really anything new to gain from this story: it's everything you've already seen (starting with Kirino's departure), just from Kuroneko's perspective. Which, even with the POV shift, is still 96% of everything we saw on the show, truth be told—and, fair warning, most of the book is reliant on that fact.
You see, Kuroneko's value is as a supplement to the Oreimo story, and it assumes quite heavily that you've already gotten through that one—and clearly remember it's details. Context, even within the handful of fully contained storylines in this series, is minimal at best. So, if you are somehow new to this world, it's gonna lose you. Like, fast.
Which, if nothing else, is disappointing. And, yes, while I was hoping for a spin-off not unlike Nagato Yuki-chan that offered a new exploration—if not a new version—of the Kyosuke/Kuroneko relationship arc, it was not so blinding a desire that I would not have accepted something else. But I was definitely not prepared for a mere rehash with an alternate ending (...um, spoiler? That’s not really a spoiler, right?).
And, yes, there’s an alternate ending for our leading lady. But, like much of the rest of the story, it lacks context—which is especially strange, given that it is, really, the lone departure from canon.
Specifically, there’s no bridge between the way things unfold in the original and how they resolve in this book. Things are just different, with no indication of why and certainly no hope of actually seeing the scenario that led to the alternate ending. In fact, the penultimate chapter leaves the characters in a place where the alternate ending doesn’t even appear to be a possibility. So, where the final chapter would, on its own, seem a perfect epilogue to a Kuroneko-centric version of Oreimo, it is very much a non-sequitur, in context.
That said, it's still enjoyable, still worthwhile if you were ardently Team Kuroneko (and why wouldn’t you be?) and are in the mood for some nostalgia and a little bit of wish fulfillment.
But, if it’s all new to you, it’s a definite pass.
At least, until you check out Oreimo. (And, y'know, get hip to who really was best girl.)