We recently ran this scenario in one of our gaming sessions. To add extra spice and fill out the story, I have created extra flavour text and written a back story.
The back story section is not to be read out to the investigators, except maybe after the game.
The flavour text for any particular room should be read out each time an investigator enters that room for the first time. Any skill tests required as part of the added flavour text are only attempted once by the first investigator to enter the room.
I hope that this is useful to you all.