I think Philip Roth intended this for two very different classes of reader: those who are driven by the author's basic drives and those in the next house over who are always laughing at him.
Whether or not Roth had any serious reasons for writing the book, it is sometimes very, very funny. And that's even before it turns into Seinfeld-level kvetching at every lover's idiosyncrasies. Still, Portnoy's last date at the end of this two-reel drive-in suggests it's never appropriate to laugh in the middle of class, or that Roth decided ridiculing Portnoy was the safest route back to society. So as not, he says, to be "ghetto".
There are also parallels to an unbearably loyal, spoiled and much-regarded son who inevitably(?) becomes a show-off. Master of the fast patter from just left of center field, pumped out regular as classwork in the northeastern U.S.
From page 247: "If I could be somehow sprung from this obsession with fellatio and fornication, from romance and fantasy and revenge -- from the settling of scores! the pursuit of dreams! from this hopeless, senseless loyalty to the long ago!"