I can't stop reading this series. I keep thinking "one more book and I'm done" but then I want the next one and then again the next one. As we've concluded in online Romancelandia: This series is crack. 
 LU is an awesome addition to the series. Manny's story! Payne's story! Best of all, NO ANNOYING LESSER POV!!! It introduces a dangerous new enemy, and new developments with the lessers. Not to mention other interesting developments. So I totally have to read the next book...