Meyer begins his forward to the reader by claiming that the “free knightly art of combat” hasn’t been previously published. While the various manuscripts certainly don’t qualify as being “published”, there were certainly other published fencing manuals that predate him.
One would be tempted to speculate that he is referring to the style taught by the Freifechter or Free Fencer guild. However, he says that all other free arts have been published, so that seems a bit odd.
Perhaps he means that no Germanic fencing manual has been published thus far. Looking through Wiktenauer, it appears that everything before Meyer was in manuscript form.
Moving on, he states that the art of combat must be learned primarily through practice. But that said, there are good reasons for learning from a book.
The Three Reasons for Learning from a book
The first reason is that it is easier to memorize and think about the art when it is assembled, written out, and presented in proper pedagogical order than it is when only presented orally in a piecemeal fashion.
The second is that it frees up more time to study the other topics the student must devote his attention to. Certainly this is just as much a concern today as it was in his day.
The third reason is that it allows the student to refresh his memory, as he certainly can’t have a master with him at all times to guide his daily practice. Without a written reminder, the student is likely to forget the greater part of the art he was taught.
Side note: these reasons are why my club produces study guides for its core classes. I’ve personally lost too much of the art due to an inability to memorize my lessons or take as thorough notes as required.