I recently did some book reviews for the ASP Alliance (which will be throwing up a SQL Server Reporting Services portal in the near future).

The reviews are for (links are to the reviews):
Hitchhiker's Guide to SQL Server 2000 Reporting Services
The Rational Guide to SQL Server Reporting Services

The reviews were easy to do as both books are excellent in their own spheres. Honestly, if you could only ever own two SRS books these would be excellent choices.