The second book by Charles Williams shows many of the unique qualities that stood out in the first, and it is better written and easier to read, yet it just gets three stars from me while the first got four. There's a lot to like here: a supernatural artifact that is a character rather than a MacGuffin; a resolution that is more along the lines of virtue and spirit than it is about cleverness and brawn, in fact, that is more about weakness than it is about strength; and some very interesting theology to chew on behind the typical thriller twists and turns, so that it feels more like George MacDonald than anyone else despite some superficial differences. But it's not as much of a step forward from the last book as I feel like it should be, and so for all the plusses I just listed it seems like Williams's sophomore slump. (Complicating all this is that I haven't been able to read like I should for a few weeks and that fragmented my appreciation of the narrative, which can't be helped.)
Behind all this is a fascinating story that I'm convinced, in the right hands, could make a great movie that has many ordinary Hollywood aspects but is done differently, in ways that make the cliches fresh again. But I can't see Hollywood ending it like this ends (and I like very much how this book ends). Still, in the right hands, Charles Williams may be able to enjoy a movie renaissance. For now, the books will remain our little secret.
In addition: Owen Barfield's ideas show up very clearly in one passage identified with Lord Arglay (a protagonist). There's some deep thinking to be done about the evolution of ideas among the Inklings and Williams may have played a central role in that.