NORMAN MAILER, eat your heart out. You had your chance and you blew it.

Truman Capote, you lucky wordsmith, you're on a roll. Because now that Norman has copped out, the gift package is being offered to you. And how much is it worth? A million? Ten million? Believe me--and You-know-who, Truman--the sky's the limit. This one is going to make In Cold Blood look like small change.

Because You-know-who--and that's all the name you'll get from him right now--has put the whole thing down in black and white, every fascinating little how and why. More than 200 pages of it, all scribbled down in one long sweaty session at the kitchen table. Forty- seven murders planned, one for each year of You-know- who's life, 23 already committed, but even at this almost halfway mark it seems time to start cashing in. So all it needs now, Truman, is for you to shape up that raw material nicely for the editors, and then you split the take with You-know-who. And remember that this is no rinkydink one-shot that happened in some farmhouse out there in country music territory. We're talking 23, Truman, and we're talking New York City. The borough of Manhattan, no less, the core of the Big Apple.

But, friends, there seems to be a Catch-23 to all this, because an author named Gordon Lish in a novel titled Dear Mr. Capote has already got it all down for us, every word of those 200-odd pages. And in so doing has made a subtle and profound, dreadful and wonderful addition to the literature of mass murder.

There is also one small Catch-23-and-a-half I must deal with before getting down to the bloody meat of the matter. Midway through the book I found myself troubled by its epistolary form. Ironically, its language so perfectly captures the whole complex nature of You- know-who that he could not really have written it. It is oral history, transmuted into living prose by a superb talent. It makes me wonder why You-know-who, a great one for cute little electronic gadgets anyhow, was not at his kitchen table that night, talking his heart and mind and guts out into a tape recorder.

Beyond that, however--and it costs very little suspension of disbelief to read it Gordon Lish's way--there can only be awe at the creation of this terrifyingly real You- know-who.

In his Murder for Profit, William Bolitho, grandmaster of this literature, wrote: "The mass-murderer lies to himself. Also, he is often a good family man." And, indeed, in his tormented, self-evasive, often diffuse and rambling narrative, You-know-who lies to himself, the bitter truths only accidentally bubbling to the surface. And he is a very good family man. He is hardworking--a faithful employee of a bank, one of the top-ten banks as he vigorously points out--and while he and his wife have their differences, he is passionately devoted to their 9-year-old son, a nice kid who, hell or high water, shortage of money being both hell and high water, is going to be brought up to have some class. As for example, that big daily calendar laid out on the desk beside his bed, so that first thing each morning the boy will see its "Word for the Day"--effectuate, capstone, impediment, whatever--and early get a grip on a high-class vocabulary. You-know-who tears off that page each morning and gets a handle on the word himself, so has come to mark his murders, not by number, but by that word of the day. He may seem the grayest of gray mediocrities when you pass him by on the street, but he has his own touch of class.

Because even the murders are no mere clumsy butcheries. The victims are always female, always dispatched by one deft blow of a needle-sharp knife through the left eyeball, the instant results of the blow sometimes disconcerting You-know-who and leading him to scientific considerations of the job done. And he is not only a thinking man but a feeling one, certain deliciously steamy--though highly relevant--memories of his past leading to quick tumescence, probably slowing down his writing a bit here and there.

"As for the contemplation of the ways and walks of these monsters," wrote William Bolitho,"--only imaginative curiosity is necessary, and as unsqueamish nerves as possible."

No one could have put it better.