I am trying to keep this very general. This means that only one name is mentioned, and that is a character first introduced in Live Free or Die along with the primary method for bootstrapping earth into a galactic power. I am going to avoid most of the technology, with a few exceptions, and give a very broad overview. I don't want to ruin the series for other people after all...
The first book was good. There were some explosions, an explanation on how humans got out of the gravity well, and the repercussions of being unable to defend ourselves. It even had some science that did sound somewhat possible (and is possible, like the SAPL) with a lot more work here on earth.
The second book expanded upon the first, and did not focus so much on Tyler Vernon, but more upon a new arrival to space. Since this book focused more on the nitty-gritty of surviving in space, it was also very realistic (except the gates...and the reaction-less drives), especially when talking about the dangers of a vacuum and orbital kinetic strikes on earth.
The third book wrapped up the entire series (unfortunately), and again it focuses upon the people who would enable earth to win a fight against aliens--in other words, the pilots, the welders, and the manufacturers--except the main character is thrown in with some horribly ineffective people.
I personally wish that there was going to be a fourth book (there is some potential there, what with the mediators being very territorial).
EDIT: According to TvTropes.org there is Word of God from Ringo that he will be continuing the series.