>LOOK
(storage closet)
This is a little-used storage closet containing odds and ends of no interest
whatsoever. The exit is to the east.
A broom is standing in the corner.
>DROP MYSTERY BOOK
Phong picks up the book and starts to read.
That's because RECURSIVE-BOOK-F only checks if Phong if he's in his room, not if that's where you dropped it:
(<AND <VERB? DROP> <IN? ,PHONG ,BUTLER-ROOM>>
<MOVE ,RECURSIVE-BOOK ,PHONG>
<TELL "Phong picks up the book and starts to read." CR>)
That's because
RECURSIVE-BOOK-Fonly checks if Phong if he's in his room, not if that's where you dropped it: