The Gordonator Precision Search Engine (GPSE) seems merely complex, but is actually extremely complex. The basic idea is to make finite categories which describe the plot, character, setting, and style of a book or movie and list those categories to users and reviewers in a logically organized hierarchical system. By making the categories finite and presenting them to the user, the user is helped because he is presented with the same list that the reviewer of the book used when the book was categorized. Also, by presenting the categories to the user, the list of options may give search ideas to the user that the user hadn't before considered.
Try it out here and see for yourself.
Of course the main site has a more basic plot search engine but it's not that good. Searching for "talking spider" did not turn up Charlotte's Web.