The Library Catalog lists all the physical books the library owns. A simple search strategy is to search the Library Catalog scope for the topic you are researching, using quotes for phrases; "business communication," "business presentations," "elevator speech," etc.
The library subscribes to two large eBook collections, which have fairly good business content. The big advantage of these collections over regular library books is that you can read these anywhere you can access the Internet. A few example titles are listed below.
The AMA Handbook of Business Writing by 
Better Business Writing, Fifth Edition by 
Brief by 
Give Your Elevator Speech a Lift! by 
Message Not Received by