I really like the series, and definitely recommend it. Admittedly book 3 has an awkward choice of narrator - I love the character and the stuff we learn about her there, and I see what SRB was trying to do with her POV, but there are a lot of scenes where she had to spy/overhear stuff in order to further the central action of the plot, and it feels...awkward at times. But they're both well worth checking out, especially if you liked the worldbuilding in the first one.

You can and should also check out <http://sarahreesbrennan.com/extras/>the short stories SRB wrote in the same 'verse and posted on her site, because they add some cool background/context and are really well done in general. I especially suggest reading "Nick's First Word" and "Sorcerer and Stone" before you start book 2.