Invincible picks up where Intangible left off, and it wastes no time getting back to the story. We learn a lot of information rather quickly, but it's never overwhelming. As I briefly mentioned in my review of Intangible, C. A. Gray does an excellent job of describing tricky scientific terms without being condescending.
I loved the plot and character development, and the author captured the teenage angst perfectly. Sometimes the second book in a trilogy can be a bit slow, but that isn't true for Invincible, which is just as fast-paced as Intangible.
I would highly recommend this series.