... but I would hardly put On Lisp in the same "gentle" category as Touretzky's book. A Gentle Introduction to Symbolic Computation could easily be someone's first ever programming book. Show me the person whose introduction to programming was On Lisp and I will show you either someone who got fed up real quick, or someone who is a whole lot smarter than me and the coders I know.

I would probably recommend this order:

1. Gentle Intro

2. Practical Common Lisp

3. On Lisp

You probably haven't read that one. On Lisp is an advanced book describing the use of macros.

I really wish he would do another printing. I've read the PDF but I'd love a physical copy without paying the outrageous prices they're listed for on used book sites (Amazon, eBay, etc).