Fascinating. The mystery is that this unfinished novel was ever published. Perhaps, like the recent publication of Harper Lee’s earlier work, it was due to the avarice of the publishers rather than merits of the manuscript. Dicken’s last work, he may have been unable to complete the story because it was so dreadful.
The few flashes of Dickens’ insight and storytelling break through the gloom only emphasize how far Dickens was “off his game.” We can only hope that, the revised final edition would have been better.
Because the work was unfinished, writing endings has become a literary cottage industry, see the Wikipedia article. The conventional ending suggestions seem persuasive.
For all but the hardcore Dickens fan, don’t waste your time.