Ask HN: Why On Lisp could download for FREE?

[juanfatas]

Hi. Paul Graham's great book on macros: On Lisp could download for FREE. I'm wondering why not his intro book: ANSI Common Lisp download for FREE? Because On Lisp is for certain people who have enough Lisp experience. And ANSI Common Lisp is that experience they need.

[mjn]

This is usually up to the publisher, in cases where the author has signed a traditional publishing deal.

It looks like Prentice Hall has taken On Lisp out of print. After publishers do that, they often let the author post a version online, since they are no longer selling it anyway. ANSI Common Lisp, on the other hand, is still in print.