In addition to keyword searching, or searching by title and author, you may search Bobcat by subject heading, in order to make use of the catalog's controlled vocabulary. Subject headings are assigned to published material by the Library of Congress. They can be very broad, consisting of one word, for example, graphic novels or comic books, but they also tend to link terms together, specifying what a work is about according to theme, period, geographical region, etc.
Graphic novels -- United States
Cartoonists -- United States -- Biography
Comic books, strips, etc -- United States -- History and criticism
Superheroes -- United States
Graphic novels -- Authorship
Comic books, strips, etc -- Moral and ethical aspects