One of the most common queries I receive about these books is what they're worth.
Unfortunately, I have no idea. Like a lot of ephemera collecting, the value is what someone will pay for it.
What I can tell you is this:
A vast majority of these books are filled with signatures of regular people. The signature of a well known or important purpose may increase the value, but proving it may be difficult. And remember: These books were for entertainment. It's not unrealistic to think someone would sign a famous name on a lark.
If your book has family in it, it's far more valuable to you than it is to anyone else. And it's a very unique piece of family history to have and pass down.
When looking at Ebay make sure you look at sold prices, not list prices. And take the sold prices with a big grain of salt. It's not unknown for someone to buy their own product to build a value history.
The value does usually peak between September and November due to the Halloween season and the assumption it's related to the occult (it's not).