Since call numbers group books by subject, you can browse the shelves and see books on similar subjects shelved together.
A Browser's Guide to the Reference Area bookmark shows approximate call numbers for lots of common topics. Since the call number system is the same throughout the library, you can use the bookmark to browse call numbers in the Classified Stacks too.
If you know the call numbers of a couple of relevant books, you can look at the shelves around them to see what's there.
Limits of browsing:
Bloomberg Law , LexisNexis , and Westlaw all have treatises and practice materials.
Publishers generally license their treatises to only one of these systems.
Bloomberg Law has books from Bloomberg BNA and the Practising Law Institute.
LexisNexis has books from Lexis Publishing and Matthew Bender.
Westlaw has books from Thomson Reuters and some other publishers owned by that group.