I have the autograph set 13/50 with the 31 autographs of coin makers and holos. I'm looking to add them to the book. Thought Id look for a rare copy to use rather than buy a regular one. So I think I've seen pictures of the one your describing. Its a soft cover right? Is it in good shape? I'm interested if you want to send pics. Probably just need one book unless you think set should stay together? What do you think? I think the rest of the autograph sets were done in hardback though. I respect your opinion tell me what I should do, lol. This will be an awesome collectable when done. Think about what you want for it.
Yes it is a soft-cover - It is in perfect shape, somehow (?!) - I believe many of those books were damaged in shipment, but I may be confusing it with the first hardcover edition... 🤷♂️
So... Now you are where I was a few years ago... I also thought about grabbing s sig set as well, but honestly, I never thought it would be a good idea since as you mention, those were really made for the hardcover first edition (Correct me again if I am wrong), so I didn't see them "fitting" together that well, given the size of the softcover is also smaller... I will try and pull it out of storage and see what number it is. Again, I really don't know what a fair value would be for this, but I'm inclined to ask along the lines of .1 or something... I believe that anything "Casascius" is worth much more than people are currently paying, and I think that will continue, but hey, just my own asshole's opinion ofc!
Cheers!
... So this would be a 2-book set I guess... Also, no personalized autograph(s), all generic since given the choice at the time! 
.... Super rare for sure, I often forget I even have them lol! 