What normal people call books, treatises are written by legal scholars, and typically contain a detailed analysis of a single area of law.
Treatises are often referred to by their original author: Scott on Trusts or McCormick on Evidence.
LaFave on Search & Seizure is a multi-volume treatise devoted entirely to a single amendment of the US Constitution. Give yourself a gold star if you know which amendment this is. It is a comprehensive work that attempts to list and analyze every significant statute and court opinon on this topic. The full title is: Search and seizure: a treatise on the Fourth Amendment. You can find this six-volume set in the Law Practical Skills Collection under the call number KF9630 .L297 2012.
A Hornbook is a single-volume treatise written specifically for law students. These are books that cover a single topic, but not in so much depth or detail. For example there is a hornbook that covers all of constitutional law in one volume. Hornbooks correspond to law school courses, and are designed to supplement casebooks.
There is also a series of paperback books called Law in a Nutshell. You may already own the Nutshell on Legal Research, as it is a recommended title for this course. Nutshells are short and simple overviews of an area of law. They make no attempt to be comprehensive, but instead offer a brief introduction to the topic.
These are all examples of legal treatises.
A number of treatises are shelved in the Law Practical Skills Collection, around the corner from the Circulation Desk.
The best way to find a treatise is to ASK A LAW LIBRARIAN.
You can also browse the shelves of the Practical Skills Collection.
A legal treatise does not necessarily contain the word "treatise" in its metadata, so you can't rely on finding one in the library catalog using this keyword.
As you become a more experienced legal researcher, you will become familiar with the major treatises in your chosen area of law.
WestlawNext has a Texts & Treatises collection
Lexis Advance has a Treatises filter, under Browse Sources by Category, Secondary Sources.
BloombergLaw has a Books & Treatises collection
Treatises will always have a table of contents, and they should also have an index.
For the most part treatises are complete in one volume at the time of printing. Always check to see if there is a more recent edition.
Multi-volume treatises, like LaFave, are updated with annual pocket parts, so check in the back of the book to see if there is one.
Legal Research in a Nutshell, pp. 36-42.