It had been a long long time since I read Delirium so the beginning of Pandemonium, I felt a little lost. I liked how there was the "now" and "later" that each kind of chapter had (can't remember if Delirium did that). 
 I really liked the ending! Now that is how an ending of the 2nd book in a series is suppose to end because I can't wait to finish up the series.