For your project, you may want to use articles because they tend to be shorter and more focused than a book. However, books can be a great source of background information.
To find books written in Spanish, you can use Spanish words or you can search using English words and limit your results to Spanish language.
Some helpful keywords:
novela negra
novela policial
Latin America and detective fiction
Go to the BGSU Libraries Catalog and do some subject heading searches:
Detective and mystery stories -- Bibliography
Detective and mystery stories, Argentine -- History and criticism
Detective and mystery stories, Cuban -- History and criticismDetective and mystery stories, Latin American -- History and criticism
Detective and mystery stories, Mexican -- History and criticism
Detective and mystery stories, Portuguese -- History and criticism
Latin American fiction -- 20th century -- History and criticism