Ack! What was wrong me that I waited 4 (!) years to pick this one up after I read book 3?! I remembered enough of the basic plot that I was able to quickly pick right up and get into it. I enjoyed Theo and Selena's story. I liked that Selena is a bit older than the average heroine (she is 50). Some questions answered (like how the Ganga's or zombies are created/made and what (or who) they used to be. I liked the pop culture references (however that will really date this book (and series) for anyone reading this in, say, 50 years from now).
I won't be waiting so long to read book 5 (Night Forbidden) and book 6 (Night Resurrected). Recommended for fans of post-apocalyptic dystopian books. Series should be read in order.