Without even thinking about it, I put down my fork and said "Be careful!" Then I backpedaled. What I meant to say was "Of course you can run it by her, but (I suggest) only after you've worked it through." I urged the author to work with me to develop the idea and make a wonderful case for it. The art of writing a full-featured nonfiction book proposal and sample chapter would help the author determine whether he loved this particular idea enough now to take it all the way to a book, and it would also demonstrate that book's essentiality in document form that an agent could then see.
In my experience, agents can be professional naysayers when it comes to new literary projects. For them, new books mean more work with little hope of monetary reward unless the project is highly commercial or fits a specified niche. "No" is the easiest answer in a world where "yes" means having to babysit the author through an idea that may not get off the ground. Yet by definition, most work-in-progress is just that -- embryonic, shape-shifting, uncertain. Innocent authors call their agents when they get new ideas, only to hear some variant of "It will never work."
I listened to my then-agent over a decade ago when he nixed a project I was working on about having been born into a family that lost a child, and what it meant to be the child who was specifically conceived to take the place of another. Personally I have liked the role fine (we are all born in unusual circumstances, yes?), but I thought it would be worth exploring my own family and others where a devastating loss is followed by a planned new arrival. "Too much of a downer," said my agent, and it wasn't until years later that I stopped to remember that his first book -- a bestseller -- had an equally bleak theme. His "no" wasn't the considered wisdom of a literary guru at all. It was the knee-jerk response of an agent being an agent. I don't blame him for this, because now that I work with scores of agents I can see that most of them do it.
One famous agent is known for taking client calls on his cell phone that never last more than one minute, during which time he usually barks "Don't do it!" and hangs up. No fewer than three of his clients have come to me distressed over phone calls with him that went exactly the same way. Once I detected the pattern, I was able to warn the third one about him, but she didn't believe me. So she called him, and of course the same thing happened. She then came to me and said "How can he earn a living if he says no all the time?"
Neither do I, but then, maybe he knows something I don't, because he has landed a lot of bestsellers in his day. I'm curious how, and why.