I actually started this post way back in my initial reading of
The Hallmarked Man; occasionally making notes as idea occurred to me, but it quickly became clear to me that it was going to take multiple re-reads and in-depth consideration to make any sense of this. As is common in Rowling/Galbraith books, expectations were regularly subverted, but the results were both intriguing and ultimately quite satisfying.
I went into The Hallmarked Man thinking this would be a second albedo volume, following The Running Grave, which was clearly albedo with all of the baptisms, rivers, rain and cleansing showers we saw, along with Strike's own self-improvement, with his weight loss and smoking cessation. There were huge hints of this from the author's Tweets, which showed us silver ships and white swans. We were told that Dean Martin's "Silver Bells" would feature, suggesting Christmas, with snow and twinkling white lights. Even the title referred to a "hallmark"-- a stamp indicating the degree of purity in a precious metal. The scene was indeed set for a silverly-white, cold and snowy journey to purification, similar to what was seen in The Half-Blood Prince and Catching Fire.
Another reason I was fully expecting albedo was that, after Strike's nigredo-duo of Troubled Blood and The Ink Black Heart, and his albedo in The Running Grave, another albedo would fit well with the "extended play" model proposed by Kathleen on Hogwartsprofessor several years ago as a means of stretching a seven book series out to ten.
Did that come to pass? Well, not exactly.....