We knew from the day we started shopping the Newsflesh trilogy that they would probably need to be published under an open pseudonym. There are a lot of reasons for that. The easiest to spot is "avoidance of over-saturating the market"—after all, as a relatively untried author, it's probably best if I not compete with myself.* Oddly, this isn't the biggest reason, just the first.
(*Before there's a general hue and cry of "but I'm planning to buy both," I should probably explain. I know that the readership of this journal is highly likely to buy both. This is one of the main reasons that I love you. The Internet readership I already have is a large portion of why we knew it would have to be an open pseudonym. It's the random bookstore browsers we're trying to avoid frightening away, the ones who won't know me from Adam until they get their hands on a copy of Rosemary and Rue or Feed.)
Genre separation is a much larger part of why I was happy to agree to writing under a pseudonym. Rosemary and Rue is fairy tale noir. It's dark, it's gritty, and it's occasionally brutal...but I would still hand it to a savvy teenager without fear that their parents would beat me to death with a baseball bat later. You could adapt the Toby books into PG-13 movies without gutting them. I won't cringe when I see high school students discussing them on my forums. Feed, on the other hand, is distopian political science fiction/horror. It has a high body count. There's gore, there's sex, there's bad language. I love it to death and consider it one of the best things I've ever written, but I so don't want you to buy it for your niece who loved Toby on the basis of my name alone. Putting a different author's name on the cover is a screaming neon sign that maybe the contents are also going to be different.
Do I expect the name to hurt sales? No. My publisher is savvy and good at what they do, and I'm really hoping this book will build a reasonable level of pre-release excitement, since it's going to be incredibly fun to do the viral marketing for. But I do expect it to make people pause and read the back cover before giving in to expectations.
So we knew I'd need a pseudonym, and after the trilogy sold to Orbit, they confirmed it. That meant we needed to pick one.
There are a lot of factors that go into selecting a good pseudonym. First off, it should be pronounceable (thus knocking my real name cheerfully from the running), and it should fall within the first half of the alphabet. That gets you a good spot on the shelf, which is important for catching the eye of the casual browser. People aren't tired of looking for something to read when they get to you. Who is Aaron Aardvark? Probably a best-seller. Your pseudonym shouldn't sound too much like the name of an author already working in your genre. We're not porn stars here. Calling myself "Maya Bone-hoff" or "Jane Hinds" isn't going to increase my sales, although it might get me slapped.
Your pseudonym should also be something you're willing to answer to in public, and don't hate. You should know what it means, since no one wants to choose "Variola Majors," thinking it's pretty, and discover later that they've just named themselves "smallpox." The Agent and I sat down and came up with a list of about twenty options, some mix-and-match, some not, all of which I was willing to live with (and all of which were somehow a complicated horror movie or television joke), and sent them to The Editor II. He gave us his preferences, we winnowed, we argued, and we settled on "Mira Grant."
"Mira" is an interesting name, in that it appears in a great many languages, always with a different meaning. The version I was looking at was from the Romany, meaning "little star." It isn't short for anything, despite its resemblance to "Miranda," and I will answer to it in public. Plus, since my real signature includes both a capital "M" and a capital "G", I shouldn't have issues during signings.
And that's why I am Mira Grant. First person to catch the horror movie in-joke in my pseudonym wins a prize (and if you already know, no hinting!).