A derivative story idea is one that has been published before. For example: “Arab terrorists hijack a jetliner and demand that their extremist leader be released or they will begin killing hostages.” Have we heard this one before, or what? Would anybody actually write such a story today? You’d be surprised.

During my years as an agent I rejected more manuscripts for lack of original story idea than for any other single reason. Other agents and editors probably experience the same thing. To restate this rule: it is absolutely essential that you do not embark on writing your novel until you are certain that your story idea has not already been published. Otherwise, you are going to waste time in a big way and end up frustrated.

What do I mean by an original story idea? Any novel based on an idea that has not been published before, or which has not been overdone on television, or in tabloids or magazines, so that the public is already tired of it, can be considered to be original.

I mean, it’s not fair, is it? Homer, Beowulf and Chaucer had it easy; those guys could write about anything they wanted because just about nothing was taken, nothing had been done. But today, just about everything appears to have been done — Gone With The Wind, War And Peace — everything. Serious problem. It’s difficult to come up with a good original idea, and very disheartening to discover that your idea already has been published.

To avoid this scenario, first, identify the genre you are writing in — mystery, romance, action-adventure, fantasy, legal thriller, medical thriller, sci-fi thriller, etc. Second, read all the novels in print in that genre and write down the story concept in each. Wow! Overwhelming. But that’s really the only way to be sure, isn’t it? You have to become familiar with the novels already published in your field of interest. Probably you already know quite a few of them; reading them is how you became interested in writing in the first place, right?

On second thought, it still sounds like a big job. I know. But really, if you’re not willing to invest the time to do your research, you cannot be serious about your work as a novelist, can you?

Well, there are a few shortcuts which might help. First, contact several friends who are avid readers of novels in your chosen field. Tell them your story idea, and ask your friends whether they have ever read a novel based on a similar idea. Be sure to engage them in a serious, detailed discussion about this, and enlist their help to track down most if not all of the recent novels that they think might be close. Begin compiling a list of the most prominent authors and the titles they have published. See how many you and your friends can think of. By doing this, you are starting to map the territory.

Second, visit a well-stocked bookstore with your trusty pad of paper or palm device in hand. Locate the various fiction sections. Now try to find all the novels in your genre-every title the store carries of that type. This will probably be a number of shelves’ worth under some section heading such as “mystery.”

Check off the authors’ names and titles that you find there against your existing list, and add all the authors and titles not yet on your list. For some genres this will be a small job; for others such as mystery it will be huge. In addition to the titles you find on the shelves, there will probably be other titles by many authors that the store does not currently stock. Usually a fairly complete list of an author’s titles will be published in a list in the front of her or his most recent book. Compile a complete list of each author’s works. Once you do this for most of the books you find, you are beginning to get the problem surrounded. Now it’s time to attack.

Find a comfortable chair in the bookstore and systematically read the back cover blurbs of every book you have found. You may be able to tell, just from the blurb, what the story idea is. If so, write down on your pad, opposite that title, a one sentence statement of the story idea. If it comes out in two sentences, that’s okay, but the more you can condense it without losing accuracy the better. (A side benefit of this exercise is to learn how to write tight little story ideas, which will be useful later in framing a powerful synopsis for submission or in-person pitches).

If you cannot determine the story idea from the back cover blurb, try reading the first chapter. If you are still not sure, read the last chapter. Usually the first or second chapters will pose the novel’s story question and the last chapter will answer it. Still not sure? Well, you’re in trouble. Try reading the first page of all the rest of the chapters in sequence until you get the concept. Hopefully somewhere during this investigation, the story idea will become clear and you can return that book to the shelf. Now go on to the next title.

A typical well-expressed story idea might be: “Dinosaurs get out of their cages and attack the people who have come to view them (Jurassic Park).” Try to keep it simple like this, but specific enough that you can tell what the story is when you read over it later.

Probably in one or two afternoons, depending on how widely you have already read in your chosen genre, and how big this genre is, you will be able to work completely through your list. Once you have done so, you should have the question of your novel’s originality accurately answered. In addition, you should have a much more detailed mental map of the field in which you have chosen to write. You have surveyed the competition, and no doubt found many interesting novels along the way. And, if you have found no story idea similar to yours, you may safely proceed to write your novel.

During this process, you might find one or more novels whose story ideas are pretty similar to yours. Don’t despair! You can make good use of this situation. First, while holding one of these similar novels in your hand, ask yourself, Is this an interesting book? From just looking at the cover (which presumably expresses the story idea in words and pictures) would you expect this book to be successful? Answer honestly and you will be to some extent describing the fate of your own novel, once it is written. What does this answer tell you? Second, ask yourself, “What can I learn from this competing novel that will make mine better?” Maybe you should buy and read this book.

But in addition, it wouldn’t hurt to take your list and this new-found knowledge back to your novel-reading friends for another in-depth discussion. Mention each title that seemed similar to your idea to your friends and see if the name jogs their memory and elicits any useful information they may have overlooked. Notice too that as a result of this field trip to your local bookstore(s), you now know a lot more about your chosen writing field. By becoming familiar with the prominent books in your genre, you have gained valuable knowledge you didn’t know you needed. I don’t know of any writer who didn’t admit to learning many important and unexpected things by completing this exercise.

Finally, a third possibility: call your library and ask for help from a sympathetic librarian or research person. (By the way, if you can find such a person, marry them.)

But what do you do if you find one or more published works with a story idea that is very similar to yours? And when you read parts of it, you realize that you couldn’t have written it better. Now what? This can pose a serious problem. The more work you have already put into your manuscript before making this discovery, the more serious the problem you have. If you have already written a lot of your novel, here’s how I would proceed.

First, take a deep breath. Don’t jump. Second, read the offending book from cover to cover to see how that author has handled your story idea. You will probably get some new ideas while reading, so make notes as you go. When you finish that book, think seriously about it. Ask yourself whether your novel is sufficiently different from the published one, or whether you need to make major changes in your work.

Maybe you will decide that the two books are not very similar after all, so you take a chance and continue writing your novel. Or you might decide that you need to make big changes and, from the notes you have taken, can see in which direction to proceed. Why not look on the bright side: maybe these changes will improve your novel!

If you decide that changes are in order, you might console yourself with the thought that writing is really just rewriting and rewriting anyway. Yeah, that doesn’t really console me either. Before you actually begin any work, try to map out the necessary changes and think through just how they would impact your book. Anything you could think of that would shorten the revision process would be welcome. In other words, think hard and act slowly. But in this situation, sooner or later you will have to bite the bullet and revise your manuscript. Knowing what I know about today’s marketplace, I would not risk catching a “derivative” label by failing to make changes. This might doom my work to the rejection pile. Good luck!