Some very usefull SAP Books
Sap R/3 Implementation Guide: A Manager's Guide to Understanding Sap
Sap R/3 Handbook
Network Resource Planning For SAP R/3,BAAN and PEOPLESOFT: A Guide To Planning Enterprise Applicatio
Writing Sap Abap/4 Programs
Administering Sap
Sap Security Clearly Explained
Implementing Sap R/3
Sap R-3 Business Blueprint
Client/Server Development with Sap's Abap/4 Development Workbench
Implementing Sap R3