Shadow of Nightis the second volume of Harkness's trilogy, and I enjoyed it just as much. It got off to a slow start, as the first 200 pages are spent on Diana and Matthew acclimating to Elizabethan life. Harkness goes into quite a bit of detail describing dress, culture, household and village functions, and all the famous people (of course) Matthew knew/knows. But once the couple gets married for the third time (yes, really), and remembers why they went to 1590 in the first place, the novel picks up quite a bit. We get a few more clues about the mystery of the alchemical book at the heart of the story, and hints at the true relationship among the different species. Diana finally comes to terms with her magical heritage and begins to learn how to control it; it was gratifying to see her regain some agency, even managing to rescue herself from the obligatory peril.
I'm greatly looking forward to the third volume, which is not yet out. Curses!