There are always Ancients. That is, discovering the secrets of wiser forebears is a common theme in fantasy novels, and happily one that I quite like. Sometimes, the Ancients are less exciting than one might hope (e.g., Robin Hobb's Elderlings), and sometimes they don't turn up at all, but the search is interesting. In Scion's Lady, Rebbecca Bradley interweaves her protagonist's personal story with Ancient discovery in a very effective way.
In the prequel, Lady in Gil, Tigrallef was introduced as an awkward, bookish type who nonetheless stands up (cautiously) for Good. The book was effective in part because it offered a more realistic approach to heroic fantasy. Scion's Lady treads a similar path, and with the same wry humor. Tigrallef sacrifices his happiness to protect his precious archives, but of course there's much more to the situation than meets the eye.
In addition to Tigrallef, Bradley keeps some characters from the last book, including Shree, Tigrallef's companion and protector. New characters are not as fully drawn, but are effective and funny. On the down side, this is largely a male-dominated series. While there are strong women, we mostly see Tigrallef's new bride Rinn, so thinly sketched to the point of caricature. She's a recurring source of humor, but the book would have been stronger had she been more fully realized.
One of the attractions of Bradley's writing is that it presumes her readers are reasonably intelligent. There's nothing overly subtle here, but she's also willing to let a joke go without hitting us over the head with it. The style is an effective balance of understatement, dry humour, and the occasional bit of slapstick.
Rather than just take gods and magic as givens, the book is an exploration of Gil's particular protector - what happened to her after her crystal housing was smashed in the previous book, how Tigrallef feels about hosting a goddess, and what to do about it. The ending weighs the potential costs of reaching an understanding.
The ending, while intriguing in concept, and emotionally balanced, fails somewhat on consistency. While Tigrallef's decisions are difficult and weighty, the logic of the resolution doesn't quite work. He and we make some interesting discoveries, but it doesn't all fit together as well as one might hope.
All in all, a very good book, and a good sequel. I'd have wished for the final resolution to be stronger, but this works well, and the writing continues to be strong, with plenty of interesting issues left to resolve.