While friends might qualify as a "cult" (ie, a group of people devoted to a particular religious ceremony) we should not let outselves become a "sect"!
What books, from any religious tradition, have we particular Quakers found, that shed light on God and God's intentions, God's interactions with the world and particular human lives, people's different experiences and understandings via whatever spiritual practices they've tried--the sort of things we as Quakers find of interest, but not necessarily from Quaker sources?