Mary Cahill's ambition -- The author sent the manuscript for ''Carpool'' to Random House with no agent

Mary Cahill — a self-confessed ”creature of the suburbs” — has created what may be the first diaper-changing detective. And Cahill’s mystery, Carpool, is the first unsolicited novel to be published by a major house within recent memory.

Once upon a time an unknown writer could send a manuscript straight to a publishing house. No more. Overwhelmed by the numbers of would-be writers, editors deal almost exclusively with projects submitted by literary agents. Cahill, 46, says she was rejected by half a dozen agents before she bundled off the manuscript to Random House herself. ”I knew I should only send a couple of chapters,” she says. ”But I just stuck the whole thing in the mail.”

Jennifer Ash, the editorial assistant who plucked the book from the Random House ”slush pile” back in the summer of ’89, knew right away she had something special. ”The title intrigued me,” Ash remembers. ”And she’d also written a witty and intelligent cover letter.” Random House bought the book and scheduled it for September 1991 publication.

In keeping with Carpool‘s crabgrass-and-carport setting, Random House has devised another first for Cahill. Instead of sending her to the usual cities to publicize her book, the firm is mounting the first-ever suburban book tour: Scarsdale, Greenwich, Winnetka, and so on. ”I told her, ‘The good news is, we’re sending you on a 12-town tour for your first novel,”’ Random House publicity director Carol Schneider recalls. ”’The bad news is, I want you to drive to all those places in your Honda.”’

Now that Cahill’s two children are grown and she is no longer ”carpooled to death,” this resident of suburban Baltimore is free to pursue her new careers as both a novelist and a copy editor. Describing the pleasures of these less demanding enterprises, she says, ”I mostly tell lies and correct other people’s grammar.”