Recommended reading for your Requirements Practice

A number of books that I use and recommend each project team to have available:

•  D. Leffingwell, et al. (2003), Managing Software Requirements: A Use Case Approach (2nd Edition), Addison Wesley
• A. Cockburn (2000), Writing Effective Use Cases, Addison Wesley
• K. Wiegers (2003), Software Requirements, Microsoft Press

There are also other books mentioned in older posts below.