I have no idea of market value. But, books of that era are not considered that old, and not necessarily valuable, though a specific one might well be. And, it's like many things. The book is only worth what someone will pay you for it. That specific book may or may not have any fans.
For example, a UK book Sex and Culture by Dr. Unwin, 1934, while of no interest to most folks, will bring many hundreds of dollars. I paid $170 for a copy which was readable but in very poor condition, because I wanted to read it. Good copies may run closer to $750. Digital copies are just plain too hard to read because of book formatting.
As a boy in the 50's, my dad used to bring home from Salvation Army novels from 1900 to 1920, things like Gene Stratton-Porter and Horatio Alger. I liked them. Clean with strong morality and the good guys finished first.
As an adult, I picked up my own copies, cheap, as I encountered them. When I retired in 1997, and knew I would be moving to Mexico, I made a permanent loan to my daughter. Her husband built a special, strong book case just for them. She was curious so investigated them online. She discovered a market value over $5000, and they put a special rider on their insurance policy.
But, note these were in good shape, and some were first editions. Also, some titles are more popular. Stratton-Porter originals have a lot of fans, for reading, not just for collecting, which is why I bought them.
I don't even remember how many I had. i think over 100 but less then 200. So, those 50 cent books are probably worth $20 or more each now.
One thing, in all my years, I never found an original Stratton-Porter non-fiction book. I bought some reproductions, but that is not the same.
My point here is being an old book may not produce any market at all. Or, you might find a real surprise.