SPRINKLED WITH RUBY DUST <i> by H.N. Swanson (Warner Books: $16.95; 151 pp.) : </i>

There is wonderfully evocative writing in this autobiography of the legendary Hollywood literary agent who represented F. Scott Fitzgerald, William Faulkner, Raymond Chandler, James M. Cain and the mysterious Cornell Woolrich (the most noir of the noir writers, upon whose story “Rear Window” was based). Unfortunately, little of it is in the body of the book. The best stuff is in the introduction by a more recent Swanson client, Elmore Leonard.

“(O)ne morning in mid-September, the phone rang and I spoke to H.N. Swanson for the first time,” writes Leonard, who started his career writing western novels. “He asked if I had actually written this offbeat novel about a guy named Jack Ryan--surprised, I suppose, because it wasn’t a Western. I convinced him that I was the author, and Swanie’s next line was one I will remember for as long as I live: ‘Well, kiddo, I’m going to make you rich.’ ”

What follows is an easy-to-read, but all too polite, narrative by Swanson that begins in a small Iowa town with a boy who loved to read and who dreamed of being a writer. Because his family was poor, Swanson began at a young age to devise ways of making money, and eventually he forged business relationships with famed writers. Fresh out of college, he took his first trip to New York and convinced Robert Benchley, Alexander Woolcott, Gilbert Seldes and even Fitzgerald to write pieces for “College Humor,” a magazine he founded.

The Hollywood stories Swanson tells are amusing but not surprising. There has been plenty written elsewhere about Harry Cohen’s crudeness and F. Scott Fitzgerald’s drinking, for example. One detailed account of a marathon negotiation could have told us more about behind-the-scenes Hollywood than a dozen of his celebrity anecdotes.

There are precious few moments in this slim volume when the “Swanie” of the introduction comes shining through. Near the end of the book he writes, “My advice to writers is don’t die. But if you do, don’t give up hope.” It’s the kind of line Leonard would be proud to give a character.