No major additions in the areas I focus on; I can't speak for the M&M sections as I don't collect those. The only addition of interest to me was the revenue counterfeit section, but that's only 2 pages.
"wine wallpaper issues"? Do you mean the high denominations with tabs... or the Smithsonian deacession auction material?
If the latter, I just did a spot check and there are no major changes in the wine stamp section from 2018 to 2019, other than RE107A and RE107B increasing in value, but those are outside my price range anyway.
However, there is one change that I profoundly disagree with (admittedly my experience in this area is limited, but based upon what I've seen and read it doesn't align with reality):
The footnote following RE59 from the 2018 edition reads as follows:
Stamps of design RE4 have an adjoining tablet at right for affixing additional stamps. Values are for examples with tablets attached. Examples with the tablets removed sell for much less. Used stamps with additional stamps tied on the tablet with cancels sell for about ten limes the values given. See Nos. RE107A-RE107D.
In the 2019 edition it has been changed to "Used stamps with additional stamps tied on the tablet with cancels sell for about five times the values given."
Cutting the value in half? They appear on the market so infrequently, and every time I've seen them at auction, the competition for built-up examples is quite spirited. They're scarce enough that even a 10x multiplier might be low for certain types. Why the reduction?
Hopefully Ron can chime in, as he's far more knowledgeable in this area than I.
With a 5x multiplier, I'll buy any and all genuine examples at full Scott. Any takers? I didn't think so...