I just finished my re-read of this book (this time on audio) and boy am I glad I re-read it! There was so much I forgot. So much happens in this book and it definitely ends with a cliff-hanger, so I'm glad that I'm ready to read book 5 now. 
 I have now re-read (this time on audio) the first 4 books in this series, but this one had a different reader than the first 3. It surprised me because I had gotten so used to the previous reader, but this one was really good! First, there were 2 readers, a guy and a girl. This was a great idea because there are so many male characters in the story. And then there were some special effects that made the voices really come to life. Well done! I am now going to read the book-book #5 and then I'm sure that I'll listen to that one, too, on audio. I LOVE THIS SERIES!!