Grimspace really hit the spot for me.
Jax is a jumper, possessing a rare gene that allows her to navigate a spaceship through grimspace. This enables the ship to move through stellar pathways at faster than the speed of light. When a ship she was navigating crashes for no explained reason, the Corp (the military/government body that controls everything) is eager to pin it on her. She's rescued from their clutches by March and his crew. March wants to use Jax's unique talents to start his own school of jumpers, outside of the Corp's control.
The narrative is written in first person and present tense. At first that struck me as odd, and I worried that it would prevent me from getting into the story. Instead it worked really well, lending a sense of immediacy to everything.
Jax is a strong, confident female lead. She has a sense of humor and a smart mouth. She has flaws and quirks that bring her to life. I really enjoyed seeing the story from her perspective.
The rest of the character's are equally fascinating. March, the leader of the crew (and obviously the potential love interest) is pretty well developed. I found his motivations and his struggle believable; he wants to be a hero and complete a quest for the greater good. Then there's Saul, the doctor, who is interested in the science behind their goals. Dina the engineer, and Loras the communications savant, were equally interesting members of the crew.
The world building is very well done. Often in sci-fi, the technical babble is the stuff a reader has to wade through to get to the real story. In this case, the technical stuff is the real story--and it's intensely interesting. The idea of grimspace and jumpers is well thought out and makes sense, but isn't explained in excessive detail.
There were a few issues with plot structure and pacing. On several occasions it seemed that the story strayed from the original conflict, jumping into a different and only vaguely related conflict. There are bursts of action all over the place, which is awesome, but it makes it hard to determine what the primary climax was meant to be. There is a central story, and that story gets told, but there are a lot of other things going on. As a result, the pace is inconsistent, and there's a disorganized feeling to the novel.
The big villain of the story is obviously the Corp as a whole. As is typical when the adversary is an entire government body, the author chooses one character to sort of represent them and serve as a more targeted villain. I'm avoiding naming this person because I don't want to spoil it. I found it a little disappointing, though, that we didn't get to see more of this person. I wanted more background, development, and motivation.
Overall: This book had some flaws, but I really enjoyed it. I liked Jax and the other characters, I loved the world building details, and I loved the entire tone of the story. Aguirre has a strong storytelling voice, and I look forward to reading more of her books. 3.5 stars.