A Classic
This is the first book on systems analysis that made sense to me, and I find this copy, bought to replace a long lost hardback, as fresh and clear as ever.
Data flow diagrams are a superb idea, clearly explained and brought to life here. Would that systems could be built this way. The other parts of structured analysis: mini-specs and data structure diagrams, now seem to me ill matched and too low-level. The exposition correspondingly drags a bit: hardly the author's fault.
You can get thirty or so pages free on the internet at http://www-sst.informatik.tu-cottbus.de/~db/doc/People/Broy/Software-Pioneers/DeMarco_hist.pdf. They give you the gist of the argument and illustrate the author's expository talents. Take a look. Then buy the book.