I spend a lot of time reading technical books and I expect that you do too. Perhaps you are sitting there nodding and saying 'Yeah, we have to keep current with the technology'. If so, lucky you. Sadly, I'm in so much in catch-up mode that I'm still struggling to absorb some of the advances first made in SQL Server 2005. I'm reasonably confident with Query Store, dynamic data masking and Hekaton, but there is just so much I don't know; and the more I read, the more awed I am by the gaps in my knowledge.
It was this thought that ran through my mind the other day when someone contacted me to say that they were throwing out some old computer books and did I want them.
Hell, yes. Good computer books never go out of date. I challenge you to write a book that is wiser, and more relevant for understanding the human elements of software engineering, than 'The Mythical Man-Month: Essays on Software Engineering' by Fred Brooks (1975). Even for SQL Server, Ken Henderson's three 'Guru's Guides' (2003) are classics that are wonderful to read, even though you have to treat quite a lot of what he says about the technology in an historical perspective.
If you read a mixed diet of books on any technology, some old, some new, you get the best of both worlds. When you're learning PowerShell, for example, the older books are better at explaining the context and the fundamental concepts, because their readers are almost guaranteed to know nothing of the topic. The more recent books are more eager to explain the latest stuff, and are less enthusiastic to gather up the readers for whom the whole topic is rather mysterious. The same seems to be true of any longstanding technology: it pays to read a classic, followed by something that brings you up-to-date.
It is foolish to insist on reading only up-to-date books on technology. Nothing beats getting the broad perspective. There is, for example, no pleasure quite like reading an old book on ALM and Business transformation techniques from the 1990s, and discovering ideas that came from Agile ten years later. This is why I have such a taste for books on technology, whatever their age. Good writing is always good writing, whenever it was done.