Safe Man's Guide published by Locksmith Ledger, no copyright date, no ISBN, 6" X 9", page count varies by volume (e.g., volume 1 89 pages, volume 3 59 pages).
The Locksmith Ledger used to produce a number of 6" X 9" booklets. They show up on both Amazon and eBay from time to time, especially on Amazon for some reason. Topics included padlocks, impressioning, master keying, short cuts, etc. One series the company published was a series of booklets on safes. There were around 30 volumes published in all for the safe man series, starting in the 1940's? all the way up to at least 1979.
I am not a safe expert by any means and can not evaluate the usefulness of the books as well as others could, but there are some obvious things in the booklets that might determine whether or not they would be useful to someone.
The interesting parts to safe work would be 1) changing combinations, 2) general maintenance and trouble shooting, and 3) opening safes when combinations are lost or the safe will not otherwise open.
Regarding the opening of safes the preference would be to open a safe with no damage or with minimal damage that could be repaired. To open a safe with no damage would involve manipulation. Not all safes can be manipulated, or a client may not want to pay for the time to manipulate safes--it is not like the movies where the safe cracker just turns the dials a few times. To open a safe with minimal damage requires drilling into the safe, as small a hole as possible to preferably see when the tumblers are in position for the lock to open. Drilling may also be done to retract relocking devices. There are also opportunities to drill to bypass locks altogether on some safes. Drilling holes in safes requires knowing where the "drill points" are. One drill point might be to retract a relocking device, another could be to view the tumblers, etc. Usually so many inches over and so many inches up or down from the spindle. The drill points are specific to the make and model of safes. Safes are often repainted, labels are lost, etc. So the first task is to figure out what the make and model of the safe is, and the next task is to learn what the drill points are for the safe. If one had an open safe of the same make and model they could figure out what those points were. For a safe that one is unfamiliar with one can either sink lots of holes in likely places, or learn from another safe man what the points are for that make and model. Getting those drill points was likely the main selling point of these booklets. Good safes are drill resistant, and even if damaging the safe was not a concern it would save much time and frustration to know where to drill.
The volumes I have (1 and 3, and presumably the rest), do not cover manipulation--there are entire books dedicated to that subject. What they cover is safe identification, maintenance and troubleshooting, and combination changing. Note that unless one is lucky, the volumes will not have drill points. These books were printed in a different era and there was an affidavit in the front of each volume. The safe man was to have it notarized then the Locksmith Ledger would mail them a separate set of papers with the drill points for the safes in each volume. It is unlikely that those papers will still be with the volume on the used book market.
Another defect of this series is that there is no cumulative index (where volume 3 would have a combined index for the first three volumes, etc.) That means that, yes, there is an article on the Gary Safe company on page 27 of volume 3, but unless one looked at the table of contents for all the volumes then good luck on figuring that out.
If a person is really into safes they may be of interest if the price is right. In volume 1, for example, there is an article on how to neutralize nitroglycerin that a would-be safe cracker left behind, and more usefully there are articles on safe maintenance and such. But as for practical books to get one started on safes there are better options out there than trying to assemble a collection of these volumes.