Having completed the book, I can say with confidence that Collar is indeed a great book. Though I do have a minor and one major issue.
It begs the question as to why we would make the Hybrids in the first place. Sure we needed sex slaves or soldiers or something, but why animal people? Couldn't they have just engineered something different altogether, something more stable and subservient? Considering they've achieved warp drive and our present is their distant past, I'd assume they'd be at least that smart about it. Really it seems like an excuse to use furries in a story. ;)
I loved the characters, and the way they reacted to each of their situations, and the plot of the story. I also liked how you showed that despite being the bad guys, there were redeeming values in them, as evidenced by Lynn, and starkly contrasted by Ramirez.
I didn't like, however, that it is physically impossible to NOT like Sam. He is so darn perfect in every way that I would go so far as to call him a Gary Stu. If you had something bad or another happen to him besides his old girlfriend dying, then perhaps I could forgive him for being too perfect. But he doesn't really lose anything. At all. He gives up nothing to gain everything he ever wanted. There's almost no character growth at all, the universe just hands him what he wants, he's impossible to hate, he's always right, and the main character is a two dimensional cardboard cutout. That is pretty much the definition of a Mary Sue / Gary Stu right there...
BUT! This is the only major problem I had with the book. Other than that, it was very good. :)
Overall, I would definitely recommend this book, and am glad it doesn't fall into the trap of using furry lingo or labeling itself as furry (which chases away potential readers who otherwise would love your work for what it is). Good job! :)