Personally, I'm using ANSI Common Lisp with Arc. I'd recommend it rather than On Lisp, as On Lisp is "a comprehensive study of advanced Lisp techniques" rather than an introduction. Maybe the tutorial is enough for you, but I quite like ANSI Common Lisp (so far).
Works for me. I am reading onlisp while I learn arc, and although I don't fully understand half the code in the book the concepts are what's important.
As an example; I think it's like chapter 25 where pg describes how one can do object oriented programming in lisp. I was able to look at his code a see how his functions became fewer more readable lines in arc, but more over I am able to start working on oo concepts even though arc doesn't have a direct map to class and superclass functions.
The really good idea would be to rewrite all the code from the book in Arc. I love the book and I don't know Common Lisp. The book would be much clearer with examples written in Arc. For example generalized variables: I didn't even read examples from the book, I read the Arc source instead.
