As title above states, what was/were the first "Opening Repertoire" book/s? I remember that opening books of the 1970s and early 1980s weren't actually repertoires for White or Black, but treatises on the various openings and defences. Now the concept of "opening repertoire" is very popular.
1939: White to Play and Win by Weaver Adams. Adams believed that 1.P-K4 (1.e4) wins by force. In this book he presents his recommendations for White against the various Black defenses. For example, against 1...e5 he recommended the Bishop's Opening 2.Bc4. He continued to revise his system and write more books, e.g., he switched from 2.Bc4 to 2.Nc3 in his 1946 book Simple Chess.
In 1561 Ruy Lopez (pronounced Rue-y Lopeth) de Segura (1530-1580) wrote Libro de la invencion liberal y arte del juego del Axedrez, por Ruy-Lopez de Sigura, clerigo, vezino dela villa Cafra. He wrote the book in response to Damiano's book. It contains 66 games. In 1584, his book was translated into Italian by Gio. Dominico Tarsia and printed at Venice by Cornelius Arrivabene. In 1655, it was translated into French and published at Brussels.
This might be the first one: "Opening Repertoire for the Attacking Player" by David Levy and GM Raymond Keene. It was first published in 1976.
Here is another in a similar format: "The Chess Opening for You: A Complete System for White and Black". It was first published in 1975.
I recall reading My System by Nimzovich. That must have predated the 1970ish books noted. Assuming repertoire means what it seems to mean otherwise PCO would have been earlier than 1970ish.
It would appear to have been a series of booklets later put into the form of a single book circa 1930s.
I still suspect there were earlier books from Italy and europe.