By the time the book ends, we see a ton of plot threads wrapped up: The slayer, Nefley, is no longer a threat (in fact, he's converted to supporting vamps); Dave and Nina finally admit their feelings for each other; and Barry and Dermid McKinnon can't keep Reuben in captivity and are totally powerless now that they're struggling with adapting to vampire life.
We also learn that what we've been reading this whole time is the memoir Nina has written about the events of the past year. Granted, she's made some changes to protect identities, so we can't be sure that any particular detail we've read about is actually true. But her faith in her ability to tell her story is pretty important here, so we'll quote the last few lines of the book in full:
So there you have it. I've tried to tell the truth, and I might have succeeded. Or then again, I might not. You'll never know, will you? At least, I hope you'll never know.
One thing, however, you can be absolutely sure of—and that's the fact that I've done my best.
What more can you expect from any normal human being? (29.77-79)
The thing that Nina's reinforcing here is that her humanity has triumphed over her vampiric side. She didn't spend the last year sitting around like a pitiful lump. Nope, she was active. She went on this crazy adventure, helped free Reuben, and had more guns pointed at her than she'd care to remember. She even helped talk a delirious Dermid down from a killing spree. In short, she took charge of her life and did the right thing.
If that doesn't help show her human side, what would? Nina's counting on her book to speak for itself, and to convince us that vamps aren't so different from humans after all.