Hello, welcome to AW!
I don't know if "most" of us use pen names, but many do for sure. So far, all of my publishing has been under my real name, which is utterly forgettable and there are several of us, even one who's published fiction with apparently about as much (read; not much) success as I have. Therefore, I intend to use several going forward: a folksy, friendly one for children's stories; a manly, chest-beating one for historical fiction; and I'm not sure about what I'll use for that I write the most of, which is mainstream contemporary. I also have several non-fiction ideas in mind, which I'll probably publish under my real name, since my real-life degrees and credentials are under my real name (of course).
You seem to know this already, but pen names are about branding, and giving the reader an accurate idea of what to expect. You know what you're in for when you pick up a Fern Michaels, James Patterson, or Umberto Eco book. I want you to know what you're in for when you pick up one of mine (which would mean I've at least been published and popular enough for you to know who I am, which has not happened--yet
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