One source of background information on the author is the SPU database Literature Resource Center. Search the Literature Resource Center by Person, as follows:
See also, at the University of Washington, . The Children's Literature Comprehensive Database provides "information about books, authors and illustrators [from] around the world", but is not available in Seattle.
This query of the Advanced Search area of the Library's discovery system will turn up biographies as well as studies that, though not called biographies, may contain at least some biographical information:
Nonetheless, you might want to start by running one of the two following searches instead, both of which will help you hone in on biographies specifically:
Here I can do little more than direct you to the two boxes above on Finding biographical information (Literature Resource Center) and Finding biographical information (biographies) and to the tab labelled Find Argument sources.
A Library discovery system Subject search like the following—tolkien in subject AND dictionaries OR encyclopedias in subject—will return author-, work-, or series-specific dictionaries and encyclopedias like those listed below. Dictionaries and encyclopedias like these can be used to look up information on a given author and the imaginary world of the text: