Fictional books from the perspective of a researcher?

Hi, as the title says I'm looking for some suggestions for a book from the perspective from some sort of researcher. It doesn't necessarily have to be in the form of journal logs or anything, I'm pretty keen on any form of 'mixed media'. Some books that I've already read that follow that theme would be:

• Emily Wilde's Encyclopaedia of Faeries by Heather Fawcett

• Piranesi by Susanna Clarke

• A Good Girl's Guide to Murder by Holly Jackson

I would prefer if it was someone researching something that doesn't exist in real life like in the Emily Wilde series with her researching faeries and stuff since I enjoy exploring fantasy/sci-fi world building from an analytical perspective – figuring out how everything works and piecing everything together. That being said, I'm not too picky with the actual subject matter as long as it is fictional in nature. Thank you!