A ton of fun, although there were some issues with layers 4 and 7. Layer 4's suggestion to split into equal sized pieces... doesn't make sense, given that the rails are intrinsically different sizes, and even the examples disprove it!
I don't know why trying to solve layer 7 didn't work, but even with the actual grid (I first tried straining my eyes to use the one in the book) and the keyword, neither myself nor dcode were able to produce the correct answer!