Query Letters

I haven't sent a query letter in years, but I've been thinking about them a lot lately. A query letter is something an author sends to a literary agent to get them to represent their work. A lot of publishing companies won't give you the time of day if you're not represented. I learned that the hard way when I was about eighteen and I noticed that Final Destination books (I still have the books, but they are more like collector's items for me. I haven't even read some of them.) were being published. I thought that I could do that, that I could write a book about Final Destination. The publishing company basically told me not to bother them unless I had an agent. When I got a little older and took a few writing lessons, I decided to try writing a query letter. I was taught to think of a query letter like a resume. I googled what to include. Things like word count, a summary of the story, and a general background about myself were suggested. I wasn't even done with my story yet and I was sending out letters. I included bits of the story with the agents that required a writing sample. The weirdest query I ever sent was through a submission form that asked me questions about my book. Each time I got either an auto-response that said no, or a personal email that said no. The worst one that I received was one which referred to me using my character's name. I gave up on querying shortly after that and started writing a new story. I wasn't sure if it was the letter or the story itself that caused me to get rejected. Probably both. I didn't know how to sell myself, and I didn't know how to sell my work. I probably still have no idea. Why would someone pick my book up out of the dozens they have out there? What's special about my work? What makes me stand out? What makes my work stand out? I think my ebook is pretty interesting, so how do I let other people know how interesting it is? I'm not considering writing a query letter now, even though I think my selling skills have gotten a little better, but I am wondering if the outcome would be different now.