World: You've read the book ...

"Millions are to be grabbed out here, and your only competition is idiots. Don't let this get around." So ran the telegram sent by the sometime playwright and Hollywood hack Herman Mankiewicz, trying to recruit a Chicago newspaperman friend to the business of writing movies. It was 1926, when screenwriters were still penning subtitles for the silents, but a Hollywood myth had been born.

Selling a screenplay remains Hollywood's answer to striking gold, the fast ticket to fame and fortune. One of the truest cliches about Los Angeles is that every poor schmuck is working on a film script, and estimates of the number written annually run to 20,000 or more. But what is Hollywood buying? It's a question agents and authors have struggled with for decades.

Howard Meibach, a 41-year-old with 20 years in Hollywood and still lacking recognition as a writer himself, now offers an answer in his Spec Screenplay Sales Directory. The book lists 750 screenplays sold "on spec", not commissioned, from 1990 to 1997. It includes, where available, the price tag and "log line", a one- or two-sentence digest prepared by readers, executives or agents. Privately printed, the book has sold nearly 2,000 copies this autumn in Los Angeles shops and via Meibach's web site, www.gotmilkstuff.com/shop/specscript.html.

The ideal log line hits the reader with an idea that is "incredibly original, and yet somehow brilliantly familiar", in the words of one producer. Meibach's personal favourite is Black Box, sold in September 1995 by a trio of writers for $800,000. (It is one of three scripts listed under the same name: aircraft crashes were a popular subject in the 1990s.)

"Local hunter finds a black box from a UFO in 1910," goes the log line. "Eighty years later, the hunter's descendants are pursued by evil aliens and the government, all trying to reclaim the box." That, says Meibach, is a perfect example of a unique, high-concept story. "You hear those two or three lines, you say right away there's a movie, most people in the business know it," he said.

A string of films that began life as spec scripts are listed in the book: Clint Eastwood's In The Line of Fire, The Rock, starring Sean Connery, and Air Force One ("Terrorist kidnaps the President's plane"). To Wong Foo (Thanks for Everything, Julie Newmar) comes with the label "Three drag queens' car breaks down in midwestern town where they interact with locals".

Almost more illuminating are the lesser-known films, or those among the 90 per cent of bought scripts that still don't make it to the screen. In Inferno City, a sci-fi thriller, "wrongly imprisoned ex-cop goes after a serial killer inside an asteroid prison". A Simple Wish ("A fairy godmother loses her magic wand") is followed alphabetically by The Sky is Falling ("Two priests go on a killing spree"). The Ultimatum, as listed, has a familiar ring. "Group of Arab terrorists threaten to detonate a bomb unless outlandish terms are met", it says. Among this year's purchases are Boudicca and The Judas Gamble ("FBI agent who is investigating a routine Washington homicide realises he is being pursued by the devil").

Most high-selling scripts are not by unknowns. Joe Eszterhas, a Hollywood titan, sold six scripts on spec for $1m or more, most notably Basic Instinct, the erotic thriller which fetched $3m in 1990. But for those who cherish rags to riches stories, there is Powers That Be, written by a 17-year-old schoolgirl, Jessica Kaplan, and sold for a reported $150,000 in 1995. The story turns on a Beverly Hills-style school where students imitate the street gang culture, "with tragic results".

Robert Stitzel, a veteran Hollywood screenwriter, is listed with his film Icarus. First offered for sale in 1980, it was rewritten and then sold for $750,000 in 1996. Bruce Willis is interested in playing the role of a veteran pilot, facing the end of his flying career, who decides to fly off with an F-15.

For unknown authors, writing a script is tantamount to playing the lottery, according to Stitzel, and "it is damn tough". Hollywood moves in fads, he says, but if you blindly follow the trend, you are likely to find that by the time the script is written, the vogue has moved on. "If someone is buying a lot of science fiction, I will write historical drama," he says.

From a reading of the book, however, there is a premium on familiar characters in unfamiliar situations. Heroic scientists, CIA and secret service agents, hitmen, pilots, cops and ex-cops, and recently, presidents, are the staples. Romantic comedies, advises Meibach, are always in fashion. And he has heard that studios are currently looking for time-travel dramas.

The good news is that nine out of 10 scripts are "really, really bad". The bad news is that a lot of bad movies get made, as in any business, because their creators have good connections.

Anyone serious about a script, Meibach urges, should get a cheap air ticket and come to Hollywood, even if just for a few days. "The failures are true heroes," he said, "not the writers that are making millions of dollars. The ones that are working three jobs, writing at night, getting up at four in the morning and writing, turning out screenplays and never giving up."