What I think to be interesting is that the book specifically mentions Hemalurgy, as it's already been established. While Steris is doing all the wedding-planning, Wax is devouring that book - and the last two sections are what intrigue me, talking about how Hemalurgy, being "good" now, should be used.
Later on in the chapter, Marasi and Wayne ask Wax what's wrong with him, and why he's been growling all the time, like he's made a bad life decision. Wayne chalks it up to the hat, but then again, it's Wayne.
And then Wax sees Bloody Tam, but nobody else does.
Basically, my idea is that Wax is using Hemalurgy. Perhaps, while reading the book, he learned how to do it, and during a fight with a criminal, perhaps, he made a spike and is using it. In HoA, we have several examples of those affected by Hemalurgy receiving hallucinations - and that could be what caused Wax to see his old enemy. Now, how this happens I don't know yet - perhaps it has to do with Miles referring to Trell (who's also mentioned in Hero of Ages, while Sazed is fixing the world, fun fact), but I suspect that we'll be learning about some more cosmere-related things related to Hemalurgy within the book. Especially considering what was in the Ars Arcanum in AoL.