It's supposed to be funny, and it is for the first fifteen pages or so, but then the constant use of 'clever' metaphors, interlinked symbols, inappropriately yet sophisticated sexual remarks and blatantly in-your-face physicality eventually wears you out. There is a somewhat detectable plot line somewhere and it does seem to involve some of the main characters but it doesn't really matter much. It's not about them, it's about the author. Of course the author himself is clever enough to understand we eventually figure that out. He therefore included a review about his own book/plot in which he explains how self-gratifying his own writing is. Clever, but it doesn't fix much. By then the damage is done.
How does it all work? What I mean by that is, what's the literary device employed here that makes us read this text without wanting to yell at the author? There seems to be a basic rule in public speaking and entertainment that if you want to say something important that people remember, then you have to say it in all seriousness. If on the other hand if you want to say something important and have people pay attention, then you need to say it with humor. In fact if you say anything funny you can make people overlook any offensive content or direct insults you wish to hide. Most stand-up comedians are living proof of this principle. Even though a lot of the content in Tetherballs isn't actually funny, it sounds funny, or we know it should be funny. That keeps our emotional brain busy enough to not see the forest through the trees.
Essentially Mark Leyner is writing about himself. He's writing about all his frustrations, desires, needs and urges. For Leyner it is not enough to weave his own needs into an intricate story with many vivid characters that each evolve and come to grips with the maddening world around them. No, Leyer quite literally screams at us through his words. I find it difficult to label any book or novel offensive because you can always decline to read it. I also find it difficult to call a novel manipulative, because we all know they are and we all willingly participate. So I wouldn't call Tetherballs offensive or manipulative because I willingly read it and I never fell for the surface text. I will call the novel sad though.