I highly recommend that you browse subject headings in the catalog -- they may locate material for you that a keyword search misses.
If you enjoy browsing the stacks, here are some call number ranges. You might also want to do a call number search within the catalog (it's like browsing the stacks, and it also includes Roanoke College books you wouldn't see here).
You can use the same searches you used effectively in the catalog (both subject and keyword), and get a lot more results! WorldCat is the closest thing there is to a universal library catalog. It includes the holdings of thousands of libraries worldwide.
Try searching the full text of books with Google Books. You’ll get results, almost guaranteed (whether they’re relevant is another story!).