I don't limit myself to conference approved literature and encourage anyone to read anything they think may help them in their recovery. Or not. It's none of my or the conference's business what any of us choose to read.
This from Fini's link:
"The term has no relation to material not published by G.S.O. It does not imply Conference disapproval of other material about A.A. A great deal of literature helpful to alcoholics is published by others, and A.A. does not try to tell any individual member what he or she may or may not read."
Here's some food for thought. There was no General Service Conference until 1951, so that first edition of the Big Book published in 1939 wasn't conference approved. Or let's go to the book. It's says right on page 87, "there are many helpful books also". I like that word "also".
-allan