I really like this book and highly recommend it.

My only complaint is that because it is so directed (you're writing a programming language and it wants to get you there very quickly) it abstracts a lot of stuff that you'll need to know if you're doing anything other than following this book. For instance, a lot of the code you write will start with

    #lang br

Instead of the usual Racket

    #lang racket

That's using some support from Racket where you say "I'm writing the `br` language" and Racket goes and runs your code in that language instead of Racket. That "language" is really just Racket with some libraries pre-included (https://beautifulracket.com/appendix/from-br-to-racket-base....) and some of those libraries are specific to the book (e.g. https://docs.racket-lang.org/br/index.html?q=br#%28mod-path....).

So if you're following along the book, the upside is that that he can skip explaining a bunch of stuff about Racket packaging and libraries. But the downside is that he skips explaining a bunch of stuff about Racket packaging and libraries. If you want to take what you've learnt here and go write a programming language in Racket, you're going to have to go and learn all of that stuff anyway. You're going to have to take apart `br` and figure out how to map its parsing stuff to Racket's and you'll find that almost none of the scaffolding from the book can be copy-pasted without including the book's libraries, and many of the concepts aren't even reuseable if you want to use Racket's parsing tools instead of the book's largely bespoke tools. (Just including the book's libraries themselves can be difficult because of how Racket's packaging works. In the New World of Racket packaging, you install a library _on your machine_, not as a dependency of your project. So if you want to run your code on another machine, you first have to manually install the library on that machine before your code can run, and Racket's tooling around this is currently very sub-par.)

But I'll say again that it's a great book and if you're interested in Lisp and Scheme in particular, you should buy it and you should read it. It's great. Just know that you'll have to read the book _and also learn Racket_.