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.
As a research library, the MU Libraries have a relatively small collection of YA literature.
More YA literature is available via MOBIUS, which includes two large public library systems. These materials can be requested online and delivered to MU.
The Daniel Boone Regional Library (our local public library) is NOT part of MOBIUS, but is located adjacent to campus at Broadway and Garth. MU students can get a public library card to check out materials and access online resources. Check out their Teens page.