Ok, so book 3 re-read and I still don't care for dystopian/post-apocolyptic settings.
My second read brings this book down to a 3.5, but I have to say, that on the second read, I was better able to appreciate the parallels to the stories of Lucifer's original battle and descent/fall. I was also better able to empathise with the tragedy and sacrifice of Baliel. So, while I got more out of it the second time around, I also found the science fiction elements even more grating, and I was totally dissatisfied with the ending. Yes, it's an HEA, but it's still lacking, with questions left unanswered, and that annoys me more than it did the first time, obviously.
I remain satisfied with the trilogy; it didn't wow me, but I feel like I got what I paid for, more or less. Perhaps someday my nieces will enjoy reading it.