Besides the fact that one of the most popular modern books teaching Common Lisp is available as an online website for free (Practical Common Lisp), introduction

Besides the fact that one of the most popular modern books teaching Common Lisp is available as an online website for free (Practical Common Lisp), introductions to popular programming languages – including a few other books on Lisp – can generally be readily found on pirate ebook communities. There are some domains where you are forced to "buy" or "borrow" books to learn, but coding is definitely not one of them.