I think one of the strengths of the American IP system is that, while you can call your ideas your own if you want to, you don't have the right to control their reproduction or distribution. To quote the 1976 Copyright Act:
"In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work."
The only way you are allowed control over the distribution of an idea is through a patent, which is only granted under certain circumstances and for a fairly limited time. This concept that ideas are not subject to individual ownership, but rather common ownership, has myriad benefits, among them the right to critique ideas and a bias toward spreading good ideas as much as possible.
Of course, in the particular case of characters and story in a book it's harder to say what is idea and what is expression of that idea. To quote wikipedia, "Courts disagree on how much of the story and characters of a copyrighted novel or film should be considered copyrightable expression."
http://en.wikipedia.org/wiki/United_States_copyright_law#Ide...