I may be too cynical, but I bet that the authors of those books didn't get paid. They were probably marked as "destroyed" in O'Reilly's accounting system.
Even if that was the case, I'll bet both of the authors would have been happy to see their books go into a library. Neither of them are currently available in Carnegie Library (our largest in Pittsburgh).
The author wouldn't get paid for a returned copy either. And publishers have very wide discretion over things like giving out freebie copies — in pretty much every standard publishing contract they control what happens to the books, not the author. An author is usually given a small amount of copies of the book (in O'Reilly's case 10) — beyond that what happens to all the rest is entirely in the publisher's hands.