A fairly rare 1938 Guide to the Appalachian Trail in Maine is up on Ebay. It is the 3rd edition which is actually the first edition that has the entire AT in Maine route. The prior second edition published a few years earlier had large sections of trail that were not built yet. The large dam on the upper Dead River (that formed Flagstaff Lake) near Mt Bigelow was not built yet and the original AT route is now underwater replaced with a section of the older Arnold Trail portage route between the Kennebec and the upper Dead River. Much of the trail especially in Western Maine originally stayed off the ridgelines going from sporting camp to sporting camp as fires on private land were not allowed. It eventually was relocated onto the ridgelines starting in the nineteen seventies. I have no financial interest in the listing, as I already have a second and third but these do not come up often. The asking price is not cheap so I expect only a few folks would be interested. I have never seen the first edition of this guide, but I have heard the Maine State Library may have one.
Post WW2 versions do come up more often as MATC used the same guide into the fifties with annual supplements.