Hi Paw Prints-

I don't think that's a silly question at all. You're right, you wouldn't want to sub a ms to a house that has already published a book for exactly the same age group, on exactly the same subject, or with the exact same story line. BUT, you can get a really good feel for the
style of book a house is looking for and sub your ms with a similar style. If you find that one house does a lot of problem solving topics for 4-6 year old kids (sharing, fear of school, fear of dentist, bullying, new baby) your ms about being the new kid in class might fit in nicely to their list. You sure can refer to one or more books on their list in your cover letter/query, stating that your ms has the same qualities as their book (problem-solving, self help, with a touch of humor, etc.). However, you should also point out how your story is
different. Show them that you've researched their list and are familiar enough with their interests to KNOW that your ms is perfect for them. If you've got a story about an alligator with a toothache, you don't want to sub to the house that has already published a book about a dragon with a toothache, or an alligator with a sore throat. But how about a giraffe with a sore throat?
Regarding your Amazon search (which, by the way, puts you ahead of the majority of writers, who DON'T bother to do that kind of research), check out those books at a book store or library. They may deal with similar topics but in a very different way. Even if a house has already published a similar topic, your fresh approach to it might be just what they'd like on their 2011 list.
I hope this is helpful to you. If nothing else, send it out and say a prayer. The worst that can happen is that they'll say no thanks! Good luck!!
Susie :D