I've scanned the first few pages of The Amber Citadel, and it appears to be in a totally different style to the Blackbird series. On her website, she alludes as much. I think you'd find Blackbird in Silver a great read, I remember enjoying it immensely. I bought each of the next three as they launched, and I've not followed series that avidly often.
Unfortunately, I lent the first four books to someone, forgot who I'd lent them to, didn't get them back, got distracted by other authors, and somehow just lost track of what Freda was up to.
It's very annoying when that happens ... and it's happened a few times.