Java RMI Resources
RMI hasn't changed that much. I think 1.3 era books will be just fine.
Thank you all for your answers I think what people said about RMI not having changed much is correct, however the tutorials could still be a bit better they gloss over some important points.
In the end the best book by far that I found, that covers some of the really good bits of RMI such as Activation was Java Network Programming and Distributed Computing.
I did look at the other O'reilly Java RMI book and in my opnion its not very good at all, for anything bigger than the smallest of RMI projects.
RMI Hello World looks nice for a start. Of course it's still a simple example, so maybe tips on RMI performance/scalability will be useful since you're already familiar with RMI.
The Java.RMI has changed very little over the years, so most of the old documentation can still be referenced. Note that one significant change is the need to compile the RMI stubs if you are using a version of Java 5.0. Most people have moved away from RMI and have embraced River (previously called Jini) for distributed systems.
If you are still thinking of moving forward with RMI then I would suggest reading the Oracle documentation or posting your questions on their forums.
As for books… Java RMI by William Grosso or Java Network Programming by Elliotte Harold.