Patricia Wrede's The Harp of Imach Thyssel is the third volume of the Shadows of Lyra omnibus, but it's not really a sequel. It shares a setting with the two previous Lyra books, but has no characters in common. The protagonist of this one is a journeyman minstrel who comes upon the powerful magic artifact of the title, and needs to handle the seduction of power, the betrayal of those who desire the harp's power, the attention of dark forces, and the uncertain intentions of mysterious characters.
It's all done quiet competently, and the story moves along nicely, but the weaknesses of the earlier books are still present here. There's one whallopingly unbelievable detail of world-building (specifically: the protagonist still treats the non-human races as legendary even though a) the first book was a big coming out party for the non-humans, b) this takes place after the first book, and c) he's familiar in detail with the events of the first book); more irritating, the central romance is still arbitrary. It reads like someone excised all the pages containing the romance itself, leaving the reader to skip from initial unspoken interest-piqued attraction to profession of undying love and marriage.
The Harp of Imach Thyssel isn't a bad book, but it's not as much better as the previous books in the series as I might have hoped, and has to be considered merely competent.