This one took too long to get anywhere. I do think that books 3 and 4 could be combined into a really tight story. 
 I like Mac's progression as a character - for me that is one of the things consistently good about this series. Mac is going through Hell, and the experience is changing her. 
 Also good is the worldbuilding and the supporting characters. 
 Not so good (other than the padding) is the cliffhanger ending. I waited to read # 3 and 4 until just before book 5 came out.