I believe, and I could be crazy and making this entirely up but I don't think that's the case here, that Naomi Novik has said that the Temeraire series is entering it's final third so it looks like this is going to be a nine book series after all, not some monstrosity that goes on forever. With that in mind I was much more cheerful by reading this book (book four, only two more before I'm caught up!) but I also just liked this one more than Black Powder War. I think it was the pacing since Black Powder War was certainly more interesting and, again this is what I think I've heard, Novik wrote the first three books back to back so it might be that she had gotten more into the swing of writing and was just a better writer by this point, she's certainly gotten a load more of experience.
Empire of Ivory by Naomi Novik
Summary: As revealed in the preview section of the last novel (and something some readers would have already guessed), the British fleet of dragons has been decimated with a horrible new illness they have no cure for. Many of the dragons are still alive but slowly wasting away, after being accidentally exposed Temerarie isn't however and that sets off a search for what gave him the immunity which leads Captain Laurence and the crew to Africa where they discover that Napoleon isn't the only person they have to worry about.
The Good: Like I said before, I liked the overall feeling of this book more than the previous one and I think it's because Temerarie and Laurence are equals by the end of this book. Even in the previous book Temerarie came off as a young person who is still trying to understand the world, by here he feels like a young person who has learned about the world and decided that stuff just isn't right and they want to change it, or at the very least defy it (oddly enough since wikipedia calls the first three books Temeraire's arc and the second three as Laurence's arc, I suppose these books will deal with Laurence coming to terms with Temeraire's newfangled ideas). It's also nice to see Novik really start to mess with history, if you're going to write a story with a game changing difference like dragons then the history should be pretty different.
The Bad: I do wonder if Novik wrote the second book and then resolved to never try and fill up all the time they crew spent on a long sea voyage again. Considering how long the book would've been otherwise I'm not going to complain, merely say that it was a surprising change. Also, despite the fact that more happened in this book than the last one (as in, advance the overall plot) it feels like not as much happened. Maybe I started speed reading and that's why it feels like less but it just didn't feel as gripping.
So, the book certainly set up a number of very interesting (and highly spoiler-y) plot threads for the next few books that I'm eager to see further explored. Wiki tells me that book seven is due out in the US sometime in 2011 so I guess I'll get the next two books finished by January or so (like I've said before, I've got a ton more books to read and some of them are HUGE, I think Inkdeath is even bigger than this one).