"Harry Potter and the Methods of Rationality" written by Eliezer Yudkowsky has become something akin to a sacred text among the rationalist community.

edit: posted is a podcast by Behind the Bastards about the Zizians, a death cult that branched out of rationalist community and which was responsible for six deaths, but it covers the rationalist community and the Harry Potter fanfiction as well.

[0]https://www.youtube.com/watch?v=9mJAerUL-7w