This is the only book on RMI that I have come across that describes the topic in depth as opposed to just providing a set of APIs. It is very complete, readable and understandable. And it also covers issues such as code mobility across different remote hosts, implementation across firewalls and exception handling.
I would suggest this is a book for designers, technical architects or those planning to implement RMI Services in systems and who need to know about the issues involved and the implications for overall design.
It is also a good read for programmers prior to writing a single line of code.
It is well written, well organised and follows a logical progression building up understanding as the reader progresses. I really do recommend this book.