tinyrb

The book is made by the creator of tinyrb (https://github.com/macournoyer/tinyrb). I've never read it, so I don't know whether it's any good, but I'm sure it's not a scam. Implementing a programming language is a pretty difficult but rewarding task. It's become a lot easier these days now that there are giant runtimes you can target (JVM, CLR and so on). I would encourage anyone who is interested to give it a shot, and to find a good book or course to do so. (That book from Brown dmunoz posted looks excellent) And once you've done that, try writing your own runtime too (garbage collector/virtual machine or native compiler). It will teach you a lot about the tools you use every day.