The major subject heading for books about literary criticism about specific works is "Criticism and interpretation." So, if you wanted to find books with literary criticism about a particular author and his/her works, you would conduct a keyword search like this:
toni morrison and criticism and interpretation
This would retrieve all items in iLink with those words in the record.
Also, a useful exercise would be to browse by subject. To do this, click on Browse, and then type in the author name and click the subject button.