he was strangely obsessed with the specific details of the cities he described characters traversing. i kinda get the feeling this was just one of those quirks, like he couldn't really abstract it in his mind. he'd be like "ok so he goes to this hotel, where the fuck is it located in the city, i need to know or i cant describe it" and just ends up planning the entire city

i remember in the shadow over innsmouth that you could probably draw a map of about this level of detail just by reading it lol