i think similarity between Common Lisp and Emacs Lisp should be pointed out more often. if you learn Emacs Lisp you have almost learned Common Lisp too. at least to the point where reading the Common Lisp Hyperspec would be a breeze

i point this out since Common Lisp is a language with huge potential for industrial applications and heavy computations. the utility of Emacs Lisp is non existent beyond emacs. of course, if you use Emacs the program to its full potential then knowing Emacs Lisp is also a huge deal