This book has been republished under a different title:

Object-Oriented Programming Languages: Interpretation (Undergraduate Topics in Computer Science)

This is an EXCELLENT read, but I wish I hadn't blown an extra $70!

I especially like the third chapter, on prototype-based languages. About time someone paid attention to those!
This book is a good survey of the implementations and reasoning behind a variety of object-oriented languages (and languages confused for OO). There's a whole lot more out there than the mongrel OO implemenations of Java and C++, and this book covers it!
If you are at all interested in OO languages in theory, check this book out! Incidentally, this is a great book in conjunction with "Programming Language Pragmatics", by Michael L. Scott (also highly recommended!).

This books gives an interesting overview of the concepts relating to object-oriented languages. Of particular interest are the discussion of prototype-based languages and the, albeit brief, discussion of reflection.
The text, however, truly requires additional editing. Problems with the text range from the simply annoying (typos, repeated words, and incomplete sentence revisions) to the severely distressing (incorrect statements and contradictions).
Though not a serious limitation, the book lacks code examples for the languages discussed. This is understandable since the focus is on concepts, but the book claims to be targeted, in part, at advanced undergraduates. I believe that code examples would be of great aid to such students if this book were used in a course. In addition, I believe that some reorganization of the material would help the presentation.