The only reference I can find to a library at Bethel follows:
Watchtower, 1962, p. 636: "...10,000-volume library are found at Bethel in Brooklyn."
Have you been there? When? How large is the room(s)? Does it contain original literature that goes back to 1879? Are members allowed to browse all of it? Are visitors allowed to browse all of it? Are visitors allowed to use a camera inside the library(ies).
Len Miller