From Merriam Webster's on line dictionary:
: an account of an unsettling or unfortunate occurrence <heard horror stories about recent layoffs>; also : something unsettling or unfortunate <his childhood was a horror story>
The themes of the stories are similar to the plot in the movie "Gaslight" at one extreme and to stories of “simple” misery, betrayal and abuse or perhaps just plain old incompetence at the other extreme.
To get an idea of the kind of material that belongs here, check out not only the stories already up, but also take a look at Rebecca Fransway's Twelve Step Horror Stories.
Don't let the careful editing of the book put you off. This is not English 101. It is a place where people can let others know what their unpleasant experiences have been with the groups. Against the benefit of warning others and helping them recognize their own situation, spelling and grammar don't count fer nuttin.