Mastering the Requirements Process second Edition. Suzanne and James Robertson. Addison-Wesley, 2006. 

"This is not only the best book on requirements gathering that I've found, it is one of the best books on *any* aspect of software development that I've ever read. It is clear, focussed, well-written, full of extremely powerful concepts, and illustrated with useful examples and formal models of all aspects of the requirements gathering process and requirements-related information. As a result, I not only gained tremendous insight into how to improve the requirements gathering process at our company, I also learned by clear example how to make best use of each of the modeling formalisms the authors recommend." Tony Stewart

Detailed treatment of how to discover requirements at linked levels of detail and write them consistently. From the perspective of innovation, this book provides the details on how to discover and define Business Events, Business Use Cases and Product Use Cases. All of these are useful inputs to the innovation process.

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