Suggestions For A World Notgeld Book?

A huge variety of notgeld was issued, but very little of it seems to appear on the market, at least in Australia.
Perhaps there is a reason for this: most of it was printed on chlorinated paper and over a period of decades, can deteriorate to the point of disintegrating.
Colour stability over the long term may also be a problem. Organic (aniline) dyes were used in the inks. That is OK, when they were only intended for a limited time and area for circulation.

For this reason, I suspect that all surving notgeld in superior condition will appreciate in value greatly in coming decades. It could well be that lots of different types of notgeld shown in a publication may no longer exist, or at least be very rare. That makes collecting very difficult, unless you are lucky enough to acquire a hoard of them.

The Coffing book is, as it's name implies, a "checklist" - it tells you which cities issued notgeld, and which broad categories of notgeld were issued in that city (municipal paper, private paper, municipal metal, POW Camp, etc). It is not, in any sense, a "catalogue". It is completely useless at telling you how many different designs and denominations were issued by each city, and almost completely useless at telling you how scarce and/or valuable a particular piece of notgeld you might have is.

You aren't going to get an all-in-one-volume "Pick-style" catalogue for notgeld, in any language. Pick left notgeld out of his paper money catalogues for a reason: there's just too much of it out there. You'd need a set of books the size of the Encyclopedia Britannica to cover it all.