Some authors spend a lot of energy trying to guess what editors want. They think about it, read books about it, ask their mentors, and ask one another. The people they tend not to ask, however, are the editors themselves, often out of a misplaced sense of propriety.
Here are some typical misconceptions:
* That you only get one chance to query an editor about your book. Not true! You asked a simple question, you didn't key someone's car or threaten their families. You can certainly ask again in the future, especially if you have significantly re-thought your project.
* That you are "out" at a press for future books if they turn down one of your pitches now. Again, nonsense! Most editors won't even remember who you are if it never got past the inquiry stage.
* That it is easier to publish at a lower-tier house than at a higher one. Actually, the opposite is sometimes true. There are exceptions, and prestige is a relative thing depending on your field and the standards for promotion at your institution, but many editors at higher-tier houses report frustration that they sometimes never even see certain projects because of erroneous author assumptions about how unapproachable those editors must be.
* That you have to hold your mouth exactly just so and submit one particular way versus another or they'll never look at it. In reality, any good editor is happy to consider a good pitch, however it arrives. Some of them don't even know what's on the publishing house website about the "rules" of submission. Most are fine with an e-mailed inquiry, and 85% of the editors I speak to want to use e-mail for everything... most don't want paper at all, although a minority still do. The ones who do will tell you after you inquire.
The bottom line is to let editors decide what editors want, and the only way to do that is to ask them. Learn to write amazingly effective, to-the-point inquiry letters that say succinctly what you're working on, how you think it fits with their stated list/press/vision, and why you're the perfect person to write this now. Then get those letters out there, to editors you admire and would like to work with. The less you second-guess editors and the more you give them the opportunity to think for themselves about your research and whether it will work for them, the better.
Oh-so-true illustration from that old internet classic, i can has cheezburger.