I was recently privileged to write 2 chapters on ISA2004 for the soon to be released SBS 2003 Unleashed book by SAMS. The first announcement that I've seen is available
The book is meant as a more advanced look at SBS post SP1.
The lead author is Eriq Neale. I am merely the author of 2 of the books 27 chapters. Great care has gone into making this book full of real how-to examples and troubleshooting by individuals with expertise in the specific area. If you are looking to learn more about ISA and SBS2003 SP1 this is going to be the book to get. Expected availability is November 22.