There are several very important reasons to come up with some comparative titles (aka "comps") for your book, all of which have to do with marketing. The marketing department - and this is true of any publisher - is not going to sit down and read your book, so it is up to you to get them the information they need to help generate publicity and sales. Your agent will also need comps to pitch your book to a publisher.
Random House has put together an excellent article on why comparative titles are important, and how they are used by marketing departments. There is a useful section at the end that describes how to find comp titles, in case you are at a loss.
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What Are Comp Titles and Why Are They Useful?
By Andrea Bachofen - Random House News for Authors
Comparison (“comp”) titles are books that are similar to yours in one of two ways: Either the content is comparable or the sales trends are expected to be similar. For your publishing team, comp titles are extremely important. The comps help editors making acquisition decisions to figure out who and how big the audience might be for a specific title. Editors also look at the sales trajectories of comp titles: Will Book X be the type of book to backlist forever, like Book Y, or go strong out of the gate and then fade fast when the publicity dies down, like Book Z? Marketing teams also find comps useful when putting together marketing plans for individual titles.
Additionally, comp titles are essential for the sales group: They give the sales reps a good shorthand when selling in to retailers. Reps have only thirty seconds to pitch each book with some accounts. Being able to say “It’s like x and y” can be one of the most effective ways to get attention from the buyer and to set expectations about audience and ballpark sales potential.
While our publishing teams often add additional comp titles during the publishing process, it is immensely valuable for them to understand what comp titles you suggest, so you can align your expectations about framing and positioning early in the process.
What Makes a Good Comp Title?
Here are a few things to ask yourself when determining if your selection is a good one:
1. Is the title recent? (Within the last two or three years is ideal.)
2. Is the title the same format? (If your forthcoming book is hardcover, don’t use a trade paperback original as a comp.)
3. Will your book have the same target audience in terms of genre? (This is relatively easy to do if the book fits neatly into a category: literary fiction, commercial women’s fiction, mystery, thriller, or science fiction. It can be more complicated if a book does not fit neatly into one category: for example, if the book is both very literary and science fiction. In that case, it is ideal to find previous books that have straddled both audiences.)
4. Does your book have the same target audience in terms of demographics? (Don’t include a young adult title if the audience for your book is clearly on the adult side, for example.)
5. Is your comp realistic and believable? (Although it’s tempting to compare your work to a breakout bestseller, it’s more credible to choose a title with a typical sales path.)
6. Has your comp been successful . . . to a certain degree? (The book doesn’t have to—and usually shouldn’t—be a phenomenon, but it should at least be on the radar of accounts or on category bestseller lists. If a comp title is a perfect editorial match but a sales failure, it may set the expectations for your book too low.)
You can read the rest of this informative article HERE.