An extensive overview of RAC. The book starts with a background of high availability concepts and earlier pre-RAC Oracle technologies, moving onto a detailed description of the architecture, then high level install and configuration instructions, ending with general concepts and guideline to follow when implementing and optimizing the RAC, DB, and application.
My only complaint would be the many lost opportunities for meaningful diagrams. The diagrams were sparse, provided little information, and occasionally didn't match the describing text.
All in all, though, the book gave exactly the information I was looking for, and it was very readable.