John Lannon was a successful author of a college writing and composition textbook. He then created various spinoffs so that his publisher could cover more markets: business writing, technical writing, and so on (for both college and high school).
So he's really not a current specialist in technical writing, and he's not employed as a technical writer. He's just an English instructor who has been using essentially the same basic materials in all his books for decades.
This text is a perfect example. It has very little to do with today's field of technical communications. There are many other textbooks that have more specific and up-to-date examples and guidelines for contemporary technical writers. Any book by Hackos, for example, runs circles around this one.
In any case, he and his publisher don't need your single-copy sale. They sell thousands of these books for coursewide use at many schools across the country for use in very elementary courses. They don't care about individual users.
So save your money and buy something else!