This User Guide is a book that provides in-depth coverage of the language. It is not a book on Object Orientation. The reader is expected to be comfortable enough with the OO concepts such as Class, Object, Relationship, Aggregation, Composition, Inheritance, Polymorphism, etc. There is the term "Unified" in UML and, as such, the mastering of a former/another OO modeling language/method is very likely to ease the switching.
The book takes UML from the beginning and provides step-by-step and in-depth coverage of the language, except for the syntax and semantics that are not all fully and equally covered. The approach is explanatory. The provided examples are quite simple and do just serve the purpose of clarifying the immediate topic under discussion or that is addressed under a chapter or section. There are no complete case examples that span over the entire book.
This book covers general UML and, as such, is definitely not a tailoring guide to specific applications. As UML is intended for any application as different as embedded real-time or databases, it's the duty of the person who bears the responsibility of methods and languages in a project to have it tailored to that specific project.
This is a book mainly intended to the UML beginners and to people who want to own a copy of the book written by the inventors of the language in their bookshelves.
I identified 11 minor typing errors in the entire book, most of them being obvious and benign incorrect references to figures.