I'm initiating an irregular issues series of bibliographic notes intended to aquaint collectors researching their collections with other references beyond Frankenhuis and the few other books or links already listed in the site's reading room. Some of the books or pamphlets are in languages other than English, primarily German, but most are well illustrated, and deciphering at least the picture captions isn't difficult. Some of the works are out-of-print, and even some in-print items may require a bit of digging to find, so where possible, I'll provide links or suggest ways of locating copies.
Klose, Dietrich.
Europas Verderben 1914 1918: deutsche und österreichische Medaillen auf den ersten Weltkrieg (Europe's Ruination 1914 1918: German and Austrian Medals of the First World War). 2016. Staatliche Münzsammlung München (State Coin Collection Munich). 346 pp. € 25.00
This is the best overall survey of the subject ever published in any language, and it should be on the shelf of any dedicated collector of WWI medals. Don't be discouraged if you don't read German: it's illustrated in sharp full color throughout, and with a little diligence and a dictionary, any reader will easily be able to understand the picture captions. This is the major reference for my collection, and it contains plenty of bibliographic material to propel further searches. It is a well produced, high quality, sturdy volume with a thread-sewn binding that will stand up to frequent use, and it is a bargain at the current price. Even if you have to pay an equal amount to have it shipped (it is a large-format, heavy book), it is worth every every penny.
This book is NOT available on Amazon or Amazon.de. Although there are probably a number of German numismatic dealers and bookstores from which it can be obtained, the following link to the Münzengalerie München online shop in Munich, where the book was published, can presently provide it at the quoted price. Like any large numismatic dealer or auction house, they have English speakers on staff who will gladly assist you with ordering:
https://shop.muenzgalerie.de/Europas+Verderben+1914+1918-+Deutsche+und+oesterreichische+Medaillen+auf+den+Ersten+Weltkrieg-+Mit+einem+Essay+von+Markus+Wesche+und+mit+Aufnahmen+von+Nicolai+Kaestner-+Klose-+D-O-A.htm