Re the noted book "Geek Love" it would seem to a natural for an interesting movie. I wonder why this never happened.
Too much special effects money to be spent?
I remember reading somewhere that David Lynch was trying to do a film version which never panned out. Seems like I also remember Tim Burton being attached to it after that but I’ll have to do some more research.
Hell how would you advertise this? I can’t remember the last time I saw even a black comedy advertised openly, so how to advertise a movie about parents intentionally deforming their own children for profit and the rivalry between said children later in life?
That…strains even the traditional definition of black comedy.
Oh and it contains incest by telepathy, which always is a crowd favorite 
Interview with the author from (I think) 1996 that mentions film adaptation.
It was made into a stage play in Atlanta about ten years ago as a joint production by a regional theatre company and the ATL based Center for Puppetry Arts. It got great reviews from some critics but also got some “WtF?” reviews from viewers, many of whom had not read the novel and weren’t expecting what they saw.