Recently, a friend of mine succinctly explained the difference between pornography and erotica: Lowbrows beat off to pornography. High-brows beat off to erotica. With the release of her album, Erotica, and her much-hyped coffee table pornography book, Sex, Madonna demonstrates just how synonymous the two terms really are.

In her latest musical incarnation, Madonna is Dita, the dominatrix persona and sex hostess of both Sex and Erotica. She intones over thumpy house beats on most of the album, which should keep DJ's mixing and remixing for months. In the title track Dita asks, "If I take you from behind/Push myself into your mind/When you least expect it/Will you try and reject it." The naughty little form/context twist is that at standard club volume, the fat bass line under this song does physically invade your body. Other audio tricks abound. "Bye Bye Baby," for instance, whips Madonna's voice into a studio-distorted baby doll. The album also features a foray "Deeper and Deeper" into discoland, as well as a paean to oral sex in "Where Life Begins." And if you ever wondered what "Justify My Love" would sound like over a house beat, it's here on "Waiting."

There are a few straightforward love songs like "Rain" and "Bad Girl," a lonely lament that echoes her Desperately Seeking Susan days. For the most part, Erotica is a first rate piece of work, although it lacks the sparkle of Madonna's earlier efforts. Musically, she's staring at the ceiling through a lot of this album, but she still puts on one hell of a show.

Part two of the Madonna's promotional bacchanalia is The Book, appropriately titled Sex. For regular readers of Playboy, Penthouse and Swank, the purchasing procedure for Sex will be remarkably familiar. The book is kept behind the counter, and you must provide positive identification to prove you're eighteen years or older, which entitles you to the privilege of laying down $50 for this piece of "erotica." The book is packaged in mylar (no peeking!), and once unwrapped, it cannot be returned--publisher's rules.

But let's say you jump through these hoops and become one of the 750,000 lucky owners of Sex. You have the spiral-bound tome in your hot little hands and you open the aluminum cover. What do you see? First, there's the safe sex disclaimer, where Madonna tells us that these delightful little tableaux represent her fantasies, which of course don't involve condoms. But if she were to ever act them out, protection is definitely on the agenda. She then introduces herself as Dita, your hostess and the hero(ine) of Sex. What follows is a written defense of pornography and a laundry list of all the naughty topics Madonna has flirted with over the last ten years. Bondage--check. Lesbianism--check. Christ imagery--check. United colors of Bennetton orgies, swimming pools, nipple ring nibbling and celebrity appearances by Isabella Rosselini, Naomi Campbell and Vanilla Ice.

It's all pretty explicit (e.g. the double page spread of Madonna's crotch) but not terribly erotic, in the sense that there's not much left to suggest. And, considering Madonna's antics in the past few years, the most shocking thing about the book is the revelation that she dyes her pubic hair, too. The half-tone black and white print quality is nothing special, and the book is somewhat flimsy--at one Boston newspaper office, the copy I saw was falling apart after less than a day (and an unspecified number of trips to the bathroom).

But the redeeming value of this book really has nothing to do with its shock value or its publishing quality. It's the splendid arrogance of Sex that really sets it apart. By publishing slick photo sex for mass consumption, Madonna, the promoter, makes a bid for America's fantasy life on an unprecedented scale. She has pushed her image as a mass media sex object to its logical extreme. This is porn-shop feminism in full bloom.

And, ideological considerations aside, this retail relay has tremendous societal value in purely economic terms. We're talking about $37.5 million retail dollars just for the book, and $20 million for the album, at the very least. Score one for market capitalism. For this alone, Madonna merits far more respect than any federally funded artist in the oh-so-chic secular high church of contemporary art. She is hawking herself on the open market instead of playing courtesan to the National Endowment for the Arts. If you don't approve of her performance or her product, you don't have to buy it. Your tax dollars aren't at stake.

She sings, "I know this is not a dining room/ Conversation/ And you don't have to listen if you/ Don't have the time." The lyric is about oral sex, but frankly, it applies equally to art. Madonna puts these products on the shelves in the same spirit as she puts her naked hitchhiker self by the side of the road in Sex. You don't have to pick her up if you don't want to. And if she leaves something nasty on the seat, you have only yourself to blame.