Add Lisp Web Tails book

free-programming-books.md

@@ -804,6 +804,7 @@ See also [TeX](#tex)
 * [Successful Lisp: How to Understand and Use Common Lisp](http://psg.com/~dlamkins/sl/) - David Lamkins
 * [Sketchy LISP](http://www.bcl.hamilton.ie/~nmh/t3x.org/zzz/) - Nils Holm
 * [Lisp Koans](https://github.com/google/lisp-koans)
+* [List Web Tails](https://leanpub.com/lispwebtales/purchases/new)
 * [Casting Spels in Lisp](http://www.lisperati.com/casting.html)
 * [Structure and Interpretation of Computer Programs](http://mitpress.mit.edu/sicp/)