Who is Alex Portnoy from Portnoy's Complaint and what is their importance?

Alex is the book's central character and its narrator. He describes himself as being in his early thirties, with dark features and a prominent nose. Publicly he is a successful socio-political advocate for the disadvantaged—blacks, the poor, the ghettoized, for example. Privately, he is obsessed with sex—he masturbates frequently, engages in anonymous sexual encounters, never stays in relationships for longer than a few weeks at a time, and in those relationships he does stay in he becomes, to varying degrees, emotionally abusive.