Jürgen, three volumes, Militaria Verlag, Vienna, 2009. (German)
This is the best source of data that I have found on Pickelhaubes.
Without question the ultimate reference source. These three volumes are produced by Verlag Militaria and are absolutely incredible. They replaced the two volume 1999 version that was absolutely impossible to find. These are better produced and a third volume has been added that is only photographs. This is done entirely in German. It is not available in English. Absolutely absolutely the go to source. The new photograph album is extremely heavy and has about 700 pages. The first two volumes on the repeats of the old two-volume Kraus. I don’t know that I would buy these if you already have the old ones as there is no significantly new data that I found. Better printing and some color. It is also somewhat cheaper at €170 for all three. If you wish to be a serious collector this is it. It does not have every answer and you will have to look further however, it is a wonderful companion to the other books by Verlag Militaria that have great photographs. It has similar line drawings to the Pietsch volumes. They seem to be the same cartoons as some older Heerskunde articles. However, this one is very well annotated, well researched, and amazingly detailed in its documentation. Time after time, I find myself going back to these books. Many of the data bits that I have in articles are referenced to these volumes. Kraus goes back to the original source and pulls the data. Now if only he would answer his e-mails…