A wealth of information about then-current information technology. Primarily, this book is about filing--a substantial portion is dedicated to the problems of alphabetizing. It may sound boring, but I thought seeing how these problems were approached was very interesting, since it's pretty easy to see how the solutions of 1974 inspired the solutions of today.
Additionally, there was a lot of really clever obsolete tech in there: magnetized index cards that spring apart at a touch like the Orange Catholic Bible, cards with holes through which rods could be inserted to select those with certain properties (e.g. all male customers by putting the rod through the 'male customers' hole on the cards), electrical devices for filing paper records, punch cards with slots for slides or microfilm so that a particular item or set of items could be retrieved... so many innovative ideas.