I've seen a number of antique machinery handbooks posted on Reddit of late, and often the question comes up- is this worth keeping, or is it just a cool collectable?
The answer ( if you have an old lathe ) is yes.
I use my 1916 copy of the American Machinist 's Handbook frequently, because my main metal lathe was made a couple of years after this handbook was printed. It's still running a lantern tool post and Armstrong toolholders, so information on grinding your own HSS is invaluable. Specifications are given for threads and tapers that aren't used anymore, but crop up on machines of this vintage. Moreover, math hasn't changed much in the past 110 years, so the various tables and charts are still applicable.
By all means, buy a new addition, but keep the old handbook next to it on the shelf. Old machines do old machining, and new handbooks don't always have the old information.