Personally, I don't think Let over Lambda and On Lisp are super advanced or hardcore. I found On Lisp very readable not too long after I got rolling with Comm

Personally, I don't think Let over Lambda and On Lisp are super advanced or hardcore. I found On Lisp very readable not too long after I got rolling with Common Lisp (after quite a few years programming experience, though). Of course, both books have great concepts that still make me muse for a moment over the nature of code. Unlike the author, I found Practical Common Lisp to be the lamp for my path into Lisp, and have no qualms about recommending it to other people.