Every so often, someone will respond to a form rejection requesting more information: feedback on the manuscript pages, more detail about why I didn't want it, maybe referral to another agent who might be interested. I don't reply to these requests (see: never get anything else done, above), because, in the coldest of terms, I don't make any money on things I've already said no to.
It's human nature to want to know why, though. Here are the three things I most commonly mean when I use the dreaded form letter, "this isn't right for my list."
1. This is not a genre I represent. As an agent, I have a tremendous amount of freedom in terms of the projects I take on; if I see something I like and I want to sell it, I am free to do so. My website bio gives a list of the genres I am most interested in, both for fiction and for non-fiction, and while I occasionally do take on something outside of my stated preferences, it doesn't happen very often. The "interests" on my website are a pretty complete list of the sorts of things I like to read. It's hard to be well-versed in absolutely every genre being published, and I find I have more than enough to keep me busy as it is.
Why this is a good thing for you: Editors, like agents, tend to specialize a bit; there are editors who only do business books, and editors who only do thrillers. An agent who specializes in the sort of books you write will, one hopes, have a good relationship with the editors who specialize in the sort of books you write.
2. This is too much like something else already on my list. This one's kind of the inverse of #1, isn't it? Let me give you an example: my client Pamela Schoenewaldt's marvelous first novel When We Were Strangers tells the story of a young Italian seamstress who immigrates to America in the late 19th century. I love immigration stories, and I love stories about Italy, so I'd happily consider taking on more of those-- but another seamstress-immigrant story is going to be much too similar. Again, I don't have time to personalize all my rejection letters, and I'm sorry to say it, but I don't owe you an explanation of why it's wrong for me-- but if you query me on a book I basically already have, it's going to be wrong for me.
Why this is a good thing for you: Publishing is a fairly small world. Pamela's editor is not going to want another seamstress-immigrant story either, so already that's one less editor in the relatively limited pool of "historical women's fiction editors" I can try. Plus you don't want to run into a "mom likes you best!" scenario, where you feel competitive with one of your agent's other clients. Better for everyone to have a fresh start with something that feels really new.
3. I didn't love it. I know how you guys think: you get a rejection letter and you think, "She HATED it!" And, okay, sometimes I really did. But just as often, I felt lukewarm about it: I liked it but I didn't love it. Sometimes the writing isn't good enough. Sometimes I take an instant dislike to one of the characters. Sometimes it's pretty good but I just don't see a sales angle for it.
Why this is a good thing for you: This is a tough business, and it's much better for you if you have an agent who feels just as passionately about your work as you do, who will really go to bat for you. Taking on a client is a significant investment of time, and I don't make any money on things I can't sell. My job is a lot more fun-- and I'm a lot more effective at my job!-- when I'm working on something that I love. Maybe I didn't love your work. So what. Go find an agent who does. You deserve nothing less.