For a paper I’m giving later this month, I was looking for the beginning of the Dutch usage guide tradition, and in particular for the first usage guide to have been published. Not every book on language qualifies as a usage guide according to the definition of the genre in Weiner (1988): such publications should deal with all aspects of language, i.e. “spelling, punctuation, phonology, morphology, syntax, and lexis, and involving sociolinguistic considerations” (1988: 173). Busse and Schröder (2009) describe usage guides as “all-in-one reference works”. This definition was the basis of my analysis of usage guides and usage problems in my book Describing Prescriptivism (Routledge, 2020).
For an earlier paper on the Dutch usage guide tradition, I focused on a work called Is dat goed Nederlands? by Charivarius (1940), which has been highlighted by Wim Daniëls in his introduction to the book’s reprint in 1998 as a precursor of the many language advice manuals that were published subsequently. A precursor, but was it the first?
To find out I checked the list of titles in an article by Marten van der Meulen in the book Language Prescription: Values, Ideologies and Identity, edited by Don Chapman and Jacob D. Rawlins (Multilingual Matters, 2020). The list does not merely comprise usage guides, but it is helpful in that it provides a variety of titles dealing with language advice – including one that may well have been the very first Dutch usage guide!

Ch.F. Haje’s book came out in 1932, and it was dedicated to … Charivarius, who was, like him, writing about language problems in the newspaper De Groene Amsterdammer. The book (like Charivarius’s later publication) was based on these pieces.
Information on Haje may be found on DBNL (though the book itself is not mentioned), such as his life dates (1873–1938), a raving review of his book in (of all places) a Dutch medical journal, and an obituary in the popular language magazine Onze Taal (1938). Some of Haje s views about linguistic correctness, the obituary reads, may have been not uncontroversial, but his commendable efforts to preserve linguistic purity are acknowledged. WorldCat only mentions a posthumous 2nd edition, published in 1945.
So – with the first English usage guide dating from 1770 and the first Dutch one, it seems, from 1932, it remains for me to find the first German publication in the field. Suggestions will be greatly appreciated!
References:
Busse, Ulrich and Anne Schröder. 2009. Fowler’s Modern English Usage at the interface of lexis and grammar. In U. Römer and R. Schulze (eds.), Exploring the Lexis-Grammar Interface. Amsterdam: John Benjamins. 69–87.
Weiner, Edmund. 1988. On editing a usage guide. In E.G. Stanley and T.F. Hoad (eds.), Words for Robert Burchfield’s Sixty-Fifth Birthday. Cambridge: D.S. Brewer. 171–183.