This was a nice sequel, with much more action intertwined with a fair amount of internal angst. While I loved all the introspection of the first book, this had a bit less and a lot more adventure.
I did like the characters. Even though I didn't really get Kara and the way she threw herself off that cliff - what, a sudden change of heart from being wacked-out crazy? . But I suppose if you have to have a bad guy, she sufficed in tandem with the doctor.
While the first book really questioned what is human, this book took a lighter view. There were characters like Dot, but the topic really only glazed the surface of the question. I think this story delved more into what will drive a person insane. How do we deal with nothingness? I've believed for years that the absence of everything defines hell. Sounds like Mary Pearson holds the same view.
I liked the ending. I didn't like it, too, but I have to admit that it was the best ending. Bittersweet, appropriate. It was realistic. The characters behaved maturely.
I don't think this rates as a story as good as [b:The Adoration of Jenna Fox|1902241|The Adoration of Jenna Fox (Jenna Fox Chronicles, #1)|Mary E. Pearson|http://d.gr-assets.com/books/1316636422s/1902241.jpg|1903936]. But I do think it's worth the read.