Yep, and after that I'd jump into PAIP, Paradigms of AI Programming.

Code: https://github.com/norvig/paip-lisp

The EPUB looks broken in my machine, try the PDF: https://commons.wikimedia.org/wiki/File:Peter_Norvig._Paradi...

Altough Scheme and CL are different paths. CL's loop it's really, really complex and Scheme it's pretty much straightforward to understand. Any advanced CL user will have to implement Scheme's syntax (and an interpreter) as an exercise for PAIP. CL in CL... well, CL is too huge, T3X tried with Kilo Lisp 23 http://t3x.org/klisp/22/index.html and I doubt if anyone can even complete anything but the few starting chapters from Intro to Common Lisp with it.

Eh, no. You have Elisp+cl-lib but SBCL too, and you can use Sly wth SBCL.

Of Lem with SBCL+Quicklisp:

https://lem-project.github.io/usage/common_lisp/

Huge tip: if you use MCCLIM, install Ultralisp first and (ql-quickload 'mcclim) later: it will give you a big speed boost. Big, not as the ones from Phoronix. Actually big. From 'I can almost see redrawing on a really old ass netbook' to 'snappy as TCL/Tk' under SBCL.

https://ultralisp.org/

As you can see, you don't need to pay thousands of dollars.

For Scheme, S9 just targets R4RS but as a start it's more than enough, and for SICP you can install Emacs+Geiser+chicken Scheme and from any Linux/BSD: distro command prompt, you run:

       sudo  chicken-install srfi-203
       sudo chicken-install srfi-216

And, as a ~/.csirc file:

      (import scheme)
      (import (srfi 203))
      (import (srfi 216))

To run SCM stuff for SICP:

       csi yourfile.scm 

or

       chicken-csi yourfile.scm

Done. Get the SICP PDF and start doing SICP. You can use Emacs+Geiser with

         M-x install RET geiser-chicken

 if you are lazy. You can install the SICP book with

        M-xpackage-install RET sicp

and read it from

       M-x info RET

and do it everything from withing Emacs by running

      M-x geiser 

(pick chicken as the interpreter). Save your Emacs settings. Done.