I immediately jumped into Murder of Crows right after I finished Written in Red because I couldn't help myself to depart from Simon, Meg, and the rest of the characters. I loved that this one introduced more -- characters like the Intuits, the human with intuition, from which cassandra sangue first born, or the increase of threats from Humans First and Last movement. The book showed that humans were no longer afraid to actually kill the terra indigene and we learned about what the terra indigene actually could do to those who hurt them.
I loved the complexity of this story, and how I couldn't exactly explain the plot because it was so rich and mesmerizing. I seriously couldn't read anything else. Oh, and on a different note, I thought Murder of Crows also provided some funny moments -- especially when it came to Simon dealing or learning about Meg -- that I didn't expect from the tone of the first book. I found those moments to be really charming.
The only complain that I could say was that maybe there were quite a number of POVs in addition to those already appeared in book #1 ... that sometimes I felt that it took away the spotlight from the 'original' casts, especially Simon and Meg.