A friend of mine read this novel “years and years ago,” probably before 2000. As he remembers it, the title may have journal or diary in it. The main character is named something like 'Luminiere', and the author may be 'Lawrence'.
As he explained the plot to me, the scientist discovers nefarious experiments, seemingly unconnected and surrealistic, (later found to be real) but puts it all together with the help of his journals.
I have searched as "Luminiere’s Diary," "Luminiere’s Journal," have tried adding the name Lawrence as the author, no luck as yet.
He adds: Somewhat more fantasy, but the core events of the novel are real. There is science, which would be advanced for the time period the novel is set in. He saves people, but I don't recollect it being a whole city or the world. The novel seems to have luminescence and gold as a focus as well.