If you don't like to use Stanza, you can also access your books via the content server using Safari, you just need to know the IP address of the computer running the calibre content server then in safari type
http://192.168.1.2:8080
Where you replace 192.168.1.2 with the IP address of your computer and 8080 with whatever port you are running the content server on (8080 is the default)