This book (and series) is awesome. It is a perfect blend of action, science fiction, romance, and fantastic characters. Jax is at the top of my list of favorite book heroines. It's amazing to watch her development throughout the series. And it is not just Jax I love; this series is full of complex and likable personalities - March, Dina, Vel.
So in Killbox, the crew is asked by the governing Conglomerate to put together an armada to stop the different threats wandering around their universe. You know - pirates, mercenaries, and the like. But their biggest threat is the Morgut. They remind me of the Reavers from the Firefly universe, not because they are the same creature, but because they are both the bogeyman of space. The Morgut like to eat people. The more they learn about what the Morgut are really planning, the more dire they realize their universe's situation is. Of course the story is bigger and much more complex than this; too much has happened throughout the four books to easily summarize here. It's definitely one of those series you need to read from the beginning and in order.
The end of the book leaves us with a cliffhanger, so I am personally glad I read the book only a couple weeks before the next one comes out. The last 20 pages left me with a headache from trying to keep myself from getting teary-eyed. It was that good!