Clockwork and Cryptography: Angelmaker Code Hints, Part 2

So here's the situation: you've read Nick Harkaway's Angelmaker, found out there's a code (!) on the American dust jacket, you've tried to solve it, and you're stuck. Presumably you've also read hints 0 and 1 here, and didn't make a whole lot of progress. In that case, you're in the right spot. Ready for hint number two? Here it is (want to have one more go on your own? Go ahead, I'll wait. If not, highlight to read):

Trust in Knopf.

 As part of the marketing campaign for the book, Knopf released a couple of images meant to help you along. I suppose if you already knew about those, this isn't a very good hint, so here's more: initially, I found this one to be especially helpful.  Later on, this one was very useful, particularly in conjunction with the image of the back of the dust jacket that I posted in part 1. 


You might also want to watch that little video clip of Harkaway talking about writing, as it does have a tiny clue in it, but if you've made it this far, it won't tell you much you don't know.

Happy codebreaking!

If you're still stuck, here's the next hint.