I'm interested in writing a novel, but it would be based on the world and creatures of another novel set. It would have none of the characters or story-line in it whatsoever. The original author would be given credit as well(and He isn't alive to ask for permission by the way). So, If I write a novel that uses the world and races of another novel and give the author of that novel full credit, is that plagiarism? I'm looking for actually facts backed up by real laws. Thanks for any help.