There is no specific subject heading for scene books. You can perform a keyword search in the catalog for the term "monologues". If you are looking for a particular type of monologue, try combining the word "monologues" with a descriptive keyword, such as: monologues and men, monologues and women, monologues and classical and monologues and contemporary, etc.
I'd recommend using the Ultimate Scene and Monologue Sourcebook: an actor's guide to over 1,000 monologues and scenes from more that 300 contemporary plays by Ed Hooks.
Use the following selected databases to connect you to play reviews.
These selected databases includes full text of plays, selected playbills, production photographs and other ephemera.
There are several tools to help you discover the collection that includes an individual play. Examples include: