Try Business Dynamics by John Sterman. I lent my copy to my brother over a decade ago. Still haven't got it back... Also Exploring Requirements: Quality Befor

Try Business Dynamics by John Sterman. I lent my copy to my brother over a decade ago. Still haven't got it back... Also Exploring Requirements: Quality Before Design by Donald Gause and Gerald Weinberg. Really useful advice about questions to ask people to understand what the system really does/should do.