I'm glad to say that last night I got a little more good news. A representative from Writers House Literary Agency liked my concept enough to ask for fifty pages and a brief synopsis. Since this makes two literary agents interested, I'm feeling much more confident that the idea is at least unique enough to get some attention. I just hope that one of them asks to read the whole manuscript.
Either way, I should have some constructive criticism one way or another, which is something I've been wanting for some time now. So far, all of my rejections have been general ones, or ones saying the agent "isn't enthusiastic enough about the concept." These sort of rejections simply mean the agent isn't interested in the genre or idea. Now, hopefully I'll have some feedback about the style of writing, etc. Please wish me luck!