> Certainly <umm> a book I wrote about the state of computing in the early 2010s--largely derived from things I had written over a few prior years--was hopelessly out of date within just a few years.

I could see it being obsolete quickly to the extent that when someone was trying to learn devops and saw a book on the (virtual) shelf that didn't cover containers next to one that did, they'd pick the latter every time. You probably saw this in your sales tanking. But I'm not sure many of the words you actually did write became wrong or unimportant either. That's what I mean by additive. And in the context of a CS program, even if their students were trying out these algorithms with ridiculously out-of-date, turn-of-the-century tools like CVS, they'd still have something that works, as opposed to fumbling because they have no concept of how to manage their computing environment.