I don't know if I have posted about comp titles before, and I know I should...
Comp titles are used to tell agents, editors, and booksellers where your
book may fit in the market or on the shelf. While not all agents ask for them, many do, and you want to supply good ones.
But good comp titles are hard to find, and not just because you've written the most special/unique/magical thing ever. They're hard because there is a set of rules around them that makes finding strong comp titles challenging.
1) You want your comp titles to be relatively recent. Usually published in the last two years.
2) You want them to be well known but not too well known. Have strong sales but not be an outlier. In other words, don't comp Harry Potter, The Hunger Games, Fifty Shades of Grey or anything else that has become a household name. Also, things that are a little less common show that you read in your genre/age group. Bonus points.
3) Don't neg your comps. It's XXXXXX except done well will not win anyone over.
4) Sometimes just comping a book doesn't provide insight, so you want to tag the specific elements that are comparable. You want your comp titles to offer a comparison to your book and to each other. So you wouldn't comp Fifty Shades of Grey to Fifty Shades Darker. But you can use comps to call out specifics like the friendships and magic of Harry Potter set against a death match battle ala The Hunger Games. Or, for fans of the historical setting of XXXXX, and the romance of ZZZZZ.
Note here: Comps don't always have to be books. Sometimes film or television make great comps, but it is usually preferred when at least one is a book. Even better if it is a book you've actually read.
Finding great comps can be hard even if you are well read in your genre, so when in doubt
- Ask your beta readers/critique partners for comp ideas