CALABASAS (CBSLA.com) — A local eight-year-old girl is now a published author, and her children’s book was launched on Wednesday.

Sienna Miller’s book, “The Adventure in Space”, is a children’s book about outer space, and is featured in the front window of the Barnes and Noble store in Calabasas. The book features twins, as she is also a twin.

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“When I saw it, I felt so nervous,” Miller said. “My favorite part of the book is when the car turns into a spaceship.

Miller kept a notebook at her side for months as she put ideas together and drew illustrations.

Miller’s mother says she was worried when Sienna would stay inside to work on her book, while other children went outside to play. However, as she says, her worry soon turned to wonder.

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“I started to look at what she had written, and I was just amazed,” Jessica Taggart said. “I’m like, ‘Oh my God, this is a whole story’.”

After four months, a company called “BookBaby”, which helps authors self-publish, came through, and Miller’s book was on it’s way to being published.

Miller donated ten of her books to Los Virgenes schools.

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Meanwhile, she has begun work on a sequel, set under the sea.