Start with the 10g RAC book from Julian Dyke, published by Apress. Then read the Oracle documentation
I am sure there are at least 1/2 dozen people madly scribbling away to get the 11gR2 RAC books out. But none have been released yet.
Book details looks very good espically the "Real World Deployments" part
--Design, implement and support complex Oracle 11g RAC environments for real world deployments
--Design, implement and support complex Oracle 11g RAC environments
--Understand sophisticated components that make up your Oracle RAC environment such as the role of High Availability, the required RAC architecture, the RAC installation and upgrade process and much more!
--Get hold of new RAC components such as ASM (Automatic Storage Management) features, performance tuning, and troubleshooting
--Deploy Oracle 11g with complex standard off-the-shelf ERP systems like Oracle EBS-
Packed with practical, real-world examples, expert tips, and troubleshooting advice on how to administer a complex Oracle 11g RAC environment
Bonus Oracle 11g RAC R2 information included