I recently came across this reprinted book in a friend's library. I hadn't seen it before, but it appears to be a refutation of the teachings of Russell and also of the Seventh Day Adventists. Some interesting logic is used by the author mainly around the Bible chronology used by Russell in his books. Even then he recognised the Bible Students were teaching falsehoods.
Interestingly (although elsewhere he says he is not being dogmatic but only suggesting) Mr Oppy concluded that the Kingdom of God would be established on the 20th day of September 1945.
I am attaching a couple of screenshots to whet your appetite if any of you want to look into it further.
https://archive.org/details/jehovahsfinished00oppy/page/6