... to find everything using this word, either search both terms, or use a wildcard. Often this is a question mark, e.g. medi?eval.
Pursuing research on medievalism could take you into the domain of many different disciplines. I've listed the main literary databases and a couple that are cross-disciplinary, but see also the list of databases by subject for databases in Art, History, Religious Studies, Theater and other disciplines.
To find books on a subject, you can do a keyword search or a subject search in the MERLIN catalog. You can also expand your search to all the academic libraries in Missouri by using the MOBIUS catalog. You can have materials from either catalog delivered to any of the MU libraries for pick-up.
Note that neither of these searches the full text of books, just a brief description. Google Book Search allows you to search within books that Google has digitized and in most cases preview a few pages. Usually a link in the left sidebar will then help you find the physical book in a library.
Book reviews may be found in most of the databases listed. Look for the advanced search feature and the option to limit by document type to review or book review.
To find overviews of how people have responded to an author, include the word reception in your search.