A: The law is on your side: you own the work the moment you create it. And legitimate editors do not steal manuscripts. It is not necessary to copyright your work through the Library of Congress. To note, you cannot copyright an idea, only your version of that idea as your original expression.
An attorney might tell you that by additionally copyrighting your work through the Library of Congress, you'd have registered proof of ownership should there ever be a question. You can then license the work to a publisher for any particular use or even transfer all rights to the publisher. Also, when the terms of the license are met, the rights in the work are returned to you. You would not have to record a transfer of those rights back to you as you normally would, which can sometimes be difficult and time-consuming.

Do what feels best for your circumstances. To note, when your book is published it will be copyrighted in your name, not the publisher's. They are only buying the rights to publish.

Many publishers, especially children's magazines and educational publishers, buy all rights to stories and illustrations. You sell all of your interest in the work and they can do with it as they please. In some cases, you can negotiate a limit on those rights such as selling first printing rights only or you can designate a timeline. Publisher guidelines usually stipulate if they buy all rights. Never sign a contract if you have any question about what exactly you are selling. See the SCBWI Publication "Copyright Facts for Writers" for more information about rights.

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