On this reading, Heir of Sea and Fire doesn't have quite the magic it did for me originally. I like that McKillip, after a first book in which Raederle appears primarily as a symbol, focuses this whole book on the women in the story. Unfortunately, that's also one of the book's weaknesses. While Raederle and Lyra are shown as strong characters, they're also clear women searching after a man. That is, they're looking for Morgon, who's important to each of them, but grouping them together this way suggests far too strongly that they're in some way auxiliary to Morgon, rather than independent actors. I doubt it bothered me when I was younger, but this time round, I found it a little uncomfortable.
The other problem of the book is a structural one. As Morgon did in the first book (and the last), the characters spend their whole time in a travelogue of the realm, visiting country after country in turn - at least the third time we've been through most of them. Yet the chase is somewhat inconclusive. There's a climax, certainly, but there's not an arc to the story so much as a direct, very linear drive. Despite McKillip's usual beautiful prose, I found the book exhausting and not really satisfying. I wish she'd focused more on Raederle's development for her own sake, and not solely as an adjunct to Morgon.
While the prose is wonderful, it also tends toward the vague. Everything is metaphor, and relatively little is concrete. It's nice to read, but often too ambiguous - it's hard to be sure what's actually happening. Still fun to read, but a somewhat rocky transitional book.