I have in my own collection an old book called "The Devil's Legacy to Earth Mortals" printed by an M. Young (I am told, courtesy of the LOC, that the "M" stands for Martin) and in it are several advertisements for other books his company makes. Some of these books I've seen for sale in old conjure catalogues, like "Old Gypsy Madge's Fortune Teller" and "The Mystery of Love Making Solved." M. Young also produced a book called "The Great Book of 400 Secrets" which was a book for household recipes (inks, soaps, etc.) and a few of the formulas he printed were called Young's _______, for example "Young's Cheng Wing Starch Polish" and he indicates within the text that he does (or did at the time) sell those Young products on his own. The Great Book of 400 Secrets can be read here.
I also have seen in certain old curio catalogues the exact cover art for Devil's Legacy, but attached to different titles -- and usually in catalogues that list other M. Young titles. I don't know if that means its the same book or not. King Curio #45 lists it with the title "The Magical Science of Black Arts" for example, right next to Gypsy Madge and the Book of Great Secrets (possibly the same as the Great Book of 400 Secrets?)
M. Young's publishing company began at least in the late 1870s, as the Great Book of 400 Secrets has a copyright of 1878 (this being the earliest date I've seen on a Young book.) According to Yronwode's page, the Young of Chinese Wash fame gave up his copyrights in 1940. If we assume he's the same man as Martin Young he'd have had to have been pretty old by that point -- probably in his late 80s at best. Now, that would make a good excuse for the fellow to sell off his copyrights rather than pay off a debt in cash, since someone that old's probably not expecting to get a lot more use out of them; but it also might be a sign that it is not the same person. Given that M. Young's books were still in print in the 1930s though, somebody was keeping up the publishing. Reportedly the Chinese Wash was sold by Oracle Products Co. and the books given up in 1940 to Joe Kay were printed by the Oracle label as well. So they weren't being printed under the publisher M. Young. This could point to a son or other relative of M. Young being the Young that ran Oracle and eventually sold off the book rights. Unfortunately I don't have any 1930s editions of the M. Young books to see who was printing them by that point.
If anyone's got some more information about either of the Youngs, send me an email will you? M. Young has been of interest to me ever since I bought that copy of The Devil's Legacy for $20 at Axis Mundi when I was in 9th grade. The possible Chinese Wash link makes things even more interesting.
EDIT: I also came on this -- http://www.arcane-archive.org/
There Yronwode says that The Devil's Legacy is the same book as Herman's Book on Black Art, and was picked up by a company called Wehman Bros. BUT -- she describes the contents of the book a little differently, suggesting maybe it's really not the same thing. She says it contains, "a straighforward history of diabolism, a respectful exegesis on mesmersism AND exposing fraud among 'manifesting' spiritualist mediums while examining their performances as a form of stage magic." But TDLTEM has nothing in it about stage magic, so that suggests maybe chapters were added in other editions.