I've always been lukewarm about this series, yet I keep reading it. Can't say it's not entertaining, of course. It's silly and funny, but emotionally, I feel nothing for it. I know, that sounds bizarre. They're fictional characters. But some authors write characters I love, want to be, want to do naughty things to and truly care about. I don't care if it sounds crazy. Bones is great. Cat's great. Vlad, et al.? Great. I don't care if they live or die. 
 Oh, plus, you definitely have to read the Night Huntress World books in between the last one and this one unless you don't care about being spoiled (and I don't...like I said, I don't care about these fictional people). But the NHW books aren't spin-offs. They're part of the series masquerading as spin-offs.