I was REALLY, REALLY HAPPY that I decided to pick these up. The storyline is tight, the action is fairly continuous, the characterizations are good. In some respects, the stories remind me a bit of the Daniel Leary stories from David Drake, which is one of my most favorite recent series.
A word of caution - There are a few fairly specific sexual references in the series (both books). They are not at all gratuitous, and they very much are integrated with and move the story along - but this is not a series for "young adults" (i.e., pre-teens).
Grimspace - Ann Aguirre
I definitely recommend starting the series with this book. Although Ann does through the obligatory character info into the second book, you really need to get the story first hand through reading this book first.
Sirantha Jax is a "Jumper," a woman who possesses the unique genetic makeup needed to navigate faster than light ships through grimspace. The concept of grimspace is kind of similar to the "sponge space" and "casimir radiation" in Drake's series, although it's implemented differently - Jax has a cybernetic implant to "jack in" to the navigation system, allowing her to sense the navigation beacons which allow FTL travel in her universe, and this requires a specific genetic mutation - where in Drake's universe, FTL travel can be taught to anyone - but only those who are truly gifted (like Leary) can wring every last advantage from it. The actual action is somewhat similar to space opera or pulp fiction (which I find very enjoyable - I want to escape into a world where the good guys always seem to squeak by), and fans of those genres should also enjoy this series.
Wanderlust - Ann Aguirre
Often the second book in a series doesn't really thrill me like the first book did, but this time I think I enjoyed both of them equally (but differently for some reason). Even though there are a lot of changes in the characters as they move through the series, the changes feel "right" and give a sense of actually moving and being human (yes, even the non-human characters feel "human" in their own right), which makes the story easier to fall into. It was kind of like watching a good science fiction movie - the detail was good enough that I could picture the action sequences as I was reading.
Edit: Note that Ann says that the genre of this series is "Romantic Science Fiction". It would probably appeal also to people who enjoy romance novels - but trust me, that's not required to enjoy this series.