I guess I just want to avoid making the whole thing a continuity spaghetti when improvising.
Yeah, I think it will be less reading ahead and more reading the current and immediately adjacent rooms description summaries. I like knowing all the puzzle pieces, but Tegel Manor has 240 rooms, that is just a little much.
Like I said just now, the Manor has 240 rooms. It is less "What was that NPC's name and what is his shop called?" and more of "In this giant web of interconnecting spaces, exactly which route did the players take, how long ago did they clear each room, and what secrets in each did they find/not find?" @ftl suggested I keep a copy of my own DM map that I can draw and take notes on, which I really like.