My newest Lyman "Reloading Handbook" is the 47th edition. However, I DO have the 2nd edition of their "Pistol & Revolver Reloading Handbook."
I can't really answer your question fairly about whether or not Lyman's Pistol & Revolver book is worth it or not because that's the one Lyman Manual I use most often. In fact, I could get by just fine without my Lyman 47 edition manual - I almost always use other company's manuals when loading for rifles. But I almost always refer to my Lyman Pistol & Revolver manual when I'm working up a load for a handgun.
I CAN answer your other question though - no, the Pistol & Revolver manual is not just a copy of handgun reloading section of the large Lyman Reloading handbook. Take the .44 magnum section for example: The big Lyman Handbook lists 13 bullets, up to 275 grains. While the 44 magnum section of the Pistol & Revolver manual lists 16 bullets, up to 325 grains. Also, the Pistol and Revolver manual includes a section of recommended Accuracy, Hunting and Silhouette loads for many of the handgun cartridges listed.
Is it worth it? Yeah, to me it is. But like I said, Lyman's large Reloading Handbook is the one I personally could live without. I guess it depends on whether you load mostly for handguns or rifles. I like Speer, Hornady and Hodgdon manuals for rifles. I mostly use my Lyman Pistol & Revolver manual, and/or Loadbooks for handguns.
I hope that helps.