Hey Srini,
You can refer to SAP Press Books by Sachin Sethi (Enhancing Supplier Relationship Management using SAP SRM) or by Ramki (Consultant Guide to SAP SRM). Both are bibles for any SRM consultant.
Also you can refer to help.sap.com pages on SAP SRM.
There are lots of material available on internet as well related to SAP SRM. You can read that as well.
Thanks
Siddarth