You can go directly to the University Book Center website and use the search under "Textbooks" for information on books. This list contains book information for all departments at the University. You will have to search for Law in the list.
It is ordered first by department (Course), then in ascending order by the 4 digit course number. You will need to have the 4 digit course number, as well as the Class Number(CRN) from your registration information in PeopleSoft to find the books for your classes. The list also indicates whether or not a book is required or optional.
If a course you are looking for is not on the list, it may be that a book order hasn't been submitted yet. The list is updated frequently prior to the start of the term and through the end of the add/drop period.
You can also access the Textbook List directly from your account on the main page of the Student Services Center in PeopleSoft at my.pitt.edu.