You may be interested in criticism on a genre or theme rather than a particular work. This can happen when there isn't alot of criticism on a specific work. Or you are interested in several similar works.
In general books will serve you better here as they are more general than articles.
You may have already encountered themes and genres when searching. You might have noticed subject headings in the records of articles and books.
Some examples:
Other (Philosophy) in literature
Race in literature
Paris (France) in literature
City and Town Life in literature
Literature and history
You can also search for criticism based on genre or critical lens. For example:
Comedy
Deconstruction
Marxist criticism
Queer theory
Structuralism (Literary analysis)