Most introductory textbooks in Operations and Supply Chain Management offer a good discussion of inventory systems. Inventory functions and drivers, independent demand models, and safety stock calculations are routinely covered in these books. One possible source:
Cecil Bozarth and Robert Handfield, “Introduction to Operations and Supply Chain Management,” Prentice-Hall, 2006. ISBN 0139446206
In addition, there are many books that deal exclusively with inventory management, some of which are decidedly more academic in nature than others.