Archives, libraries are the locations of all sorts of hidden knowledge. Borges wrote of people lost in infinite libraries. Lovecraft of reality cracking secrets being encoded in books.
For myself, libraries are a place of comfort. Nothing makes me feel more peaceful than shelves with books. But I do love stories where books are vastly more sinister and informationally dense than their reality.
Archives are where the core information of Gef appear to lie. Harry Price's archives were gifted by his widow to the University of London. A whole collection of books about magic (both stage and supernatural) that Price had collected over the years.
There is another archive: the Psychical Research Society's collection held in the University of Cambridge library. In it is apparently where the account that James Irving, the father of the family central to the mongoose story, wrote is kept.
I wonder vaguely how easy it is to access these collections, and if doing so would destroy the mystery that they currently contain. Is the desire to learn a certainty worth the loss of a multitude of fantastical possibilities?
Fictionally speaking: Harry Price may have had a copy of Lovecraft's Necronomicon in his collection. This isn't true, of course, but the possibility of this kind of connection is delicious.