By Gerald Weinberg, Dorset House, 1985, 0-932633-01-3 A short Gerry Weinberg book, which I find useful for the three laws he presents:

[p5] The First Law of Consulting: Inspiteofwhatyourclientmaytellyou,there’salwaysaproblem.

The Second Law of Consulting: Nomatterhowitlooksatfirst,it’salwaysapeopleproblem.*

The Third Law of Consulting: Neverforgetthey’repayingyoubythehour,notbythesolution.*