It's hard to know where to begin when talking about F.G.A. Dauverné's magnum opus, but its first publication in English will undoubtedly make it easier for a multitude to start the conversation.
Although roughly a third of the book is written for chromatic trumpets (the French slide trumpet and the 3-valve trumpet*), Dauverné's primary focus is on the natural trumpet.
As he states in the introduction:
"...it is impossible to become a skillful trumpeter, in any style, if one does not begin with a complete study of the natural trumpet."
...and in part three on chromatic trumpets:
"I maintain this principle, that all instruments which have had any type of mechanical addition...will never, in the end, equal the virginal sound of the natural trumpet."
Of the large volume of methods written for the natural trumpet in the 19th century, Dauverné's is by far the most comprehensive and consequential. This method is a "must have" for any trumpeter wanting to understand the foundations of modern orchestral trumpet playing.
*This 3 valve trumpet is twice the length of the modern valve trumpet pitched in the same key, essentially, a natural trumpet with valves.