Historically I've noticed that libraries are often terrible at distinguishing good from bad when it comes to technical books. Sorting through the books being thrown out, I've often found real classics mixed in with the likes of Learn Excel 98 In 24 Hours.

This also happens with used bookstores, but in that case the upshot is, instead, that used bookstores won't buy technical books, so they never make it onto their shelves.

Nowadays I almost entirely get my technical information online, in part because of having moved to Argentina, where there weren't very many technical books in the first place — our famous national abundance of bookstores are dedicated almost entirely to fiction and opinion, rather than knowledge in the sense of falsifiable propositions.